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Ccna presentation{complete]

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  • Layer 2 of 2 Note: The two commands shown in the slide can also be combined into one command: vtp domain switchlab transparent
  • Layer 2 of 2 Note: The two commands shown in the slide can also be combined into one command: vtp domain switchlab transparent
  • Layer 2 of 2 Note: The two commands shown in the slide can also be combined into one command: vtp domain switchlab transparent
  • Note: Once a port has been assigned to a VLAN, it cannot send or receive traffic from devices in another VLAN without the intervention of a Layer 3 device like a router. The 1900 can’t be configure as the VMPS. A CiscoWorks 2000 or CWSI management station or a Catalyst 5000 switch can be configured as the VMPS. In the future, dynamic VLANs may also offer membership based on other criteria such as protocol or application. Dynamic VLANs are covered in the Managing Cisco Switched Internetworks class.
  • 8 28 25 25 Purpose: Provide the student with the basic information Emphasize: Slide contents Transition:
  • Note: The 1900 only supports ISL trunking. ISL is Cisco proprietary. 802.1Q is an IEEE standard. Other trunk types: LANE (VLANSs over ATM) 802.10 (FDDI trunk)
  • Notes: VTP is a Cisco proprietary feature. VTP is a Layer 2 messaging protocol that maintains VLAN configuration consistency by managing the addition, deletion, and renaming of VLANs on a network-wide basis. VTP minimizes misconfigurations and configuration inconsistencies that can cause several problems, such as duplicate VLAN names, incorrect VLAN-type specifications, and security violations. A VTP domain (also called a VLAN management domain) is one switch or several interconnected switches sharing the same VTP domain. A switch is configured to be in only one VTP domain. You make global VLAN configuration changes for the domain by using the Cisco IOS command-line interface (CLI), Cisco Visual Switch Manager Software, or Simple Network Management Protocol (SNMP). By default, a 1900 switch is in the no-management-domain state until it receives an advertisement for a domain over a trunk link or you configure a management domain. The default VTP mode is server mode, but VLANs are not propagated over the network until a management domain name is specified or learned. If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name and configuration revision number. The switch then ignores advertisements with a different management domain name or an earlier configuration revision number. When you make a change to the VLAN configuration on a VTP server, the change is propagated to all switches in the VTP domain. VTP advertisements are transmitted out all trunk connections, including Inter-Switch Link (ISL), IEEE 802.1Q, IEEE 802.10, and ATM LAN Emulation (LANE). If you configure a switch from VTP transparent mode, you can create and modify VLANs, but the changes are not transmitted to other switches in the domain, and they affect only the individual switch.
  • Emphasize: Default VTP mode on the Catalyst switches is server. Be careful when adding new switches into an existing network. This is covered in more detail later.
  • Layer 2 of 2 Emphasize: The latest revision number is what the switches will synchronize to.
  • Emphasize: VTP prunning provides optimized flooding. Without VTP prunning, station A’s broadcast will be flooded to all switches whether they have any port in the red VLAN or not. Note: VLAN1 can’t be prunned. STP, CDP, VTP updates are sent on VLAN1. All switches in the switched network must support prunning or prunning will be disabled. Each trunk port maintains a state variable per VLAN indicating if the switch has any port assigned to a particular VLAN or not.
  • Notes: All switches in a VTP domain must run the same VTP version. The password entered with a domain name should be the same for all switches in the domain. If you configure a VTP password, the management domain will not function properly if you do not assign the management domain password to each switch in the domain. A VTP version 2-capable switch can operate in the same VTP domain as a switch running VTP version 1, provided version 2 is disabled on the version 2-capable switch (version 2 is disabled by default). Do not enable VTP version 2 on a switch unless all of the switches in the same VTP domain are version 2-capable. When you enable version 2 on a switch, all of the version 2-capable switches in the domain must have version 2 enabled. If there is a version 1-only switch, it will not exchange VTP information with switches with version 2 enabled. If there are Token Ring networks in your environment, you must enable VTP version 2 for Token Ring VLAN switching to function properly. Enabling or disabling VTP pruning on a VTP server enables or disables VTP pruning for the entire management domain. In the lab, all the switches are set to VTP transparent mode.
  • Layer 2 of 2 Note: The two commands shown in the slide can also be combined into one command: vtp domain switchlab transparent
  • Transcript

    • 1. © 2003, Cisco Systems, Inc. All rights reserved.
    • 2. 2
    • 3. 3 Data Networks Sharing data through the use of floppy disks is not an efficient or cost-effective manner in which to operate businesses. Businesses needed a solution that would successfully address the following three problems: • How to avoid duplication of equipment and resources • How to communicate efficiently • How to set up and manage a network Businesses realized that networking technology could increase productivity while saving money.
    • 4. 4 Networking Devices Equipment that connects directly to a network segment is referred to as a device. These devices are broken up into two classifications. • end-user devices • network devices End-user devices include computers, printers, scanners, and other devices that provide services directly to the user. Network devices include all the devices that connect the end-user devices together to allow them to communicate.
    • 5. 5 Network Interface Card A network interface card (NIC) is a printed circuit board that provides network communication capabilities to and from a personal computer. Also called a LAN adapter.
    • 6. 6 Networking Device Icons
    • 7. 7 Repeater A repeater is a network device used to regenerate a signal. Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuation. A repeater does not perform intelligent routing.
    • 8. 8 Hub Hubs concentrate connections. In other words, they take a group of hosts and allow the network to see them as a single unit. This is done passively, without any other effect on the data transmission. Active hubs not only concentrate hosts, but they also regenerate signals.
    • 9. 9 Bridge Bridges convert network transmission data formats as well as perform basic data transmission management. Bridges, as the name implies, provide connections between LANs. Not only do bridges connect LANs, but they also perform a check on the data to determine whether it should cross the bridge or not. This makes each part of the network more efficient. 
    • 10. 10 Workgroup Switch Workgroup switches add more intelligence to data transfer management. Switches can determine whether data should remain on a LAN or not, and they can transfer the data to the connection that needs that data.
    • 11. 11 Router Routers have all capabilities of the previous devices. Routers can regenerate signals, concentrate multiple connections, convert data transmission formats, and manage data transfers.They can also connect to a WAN, which allows them to connect LANs that are separated by great distances.
    • 12. 12 “The Cloud” The cloud is used in diagrams to represent where the connection to the internet is. It also represents all of the devices on the internet.
    • 13. 13 Network Topologies Network topology defines the structure of the network. One part of the topology definition is the physical topology, which is the actual layout of the wire or media. The other part is the logical topology,which defines how the media is accessed by the hosts for sending data.
    • 14. 14 Physical Topologies
    • 15. 15 Bus Topology A bus topology uses a single backbone cable that is terminated at both ends. All the hosts connect directly to this backbone.
    • 16. 16 Ring Topology A ring topology connects one host to the next and the last host to the first. This creates a physical ring of cable.
    • 17. 17 Star Topology A star topology connects all cables to a central point of concentration.  
    • 18. 18 Extended Star Topology An extended star topology links individual stars together by connecting the hubs and/or switches.This topology can extend the scope and coverage of the network.
    • 19. 19 Hierarchical Topology A hierarchical topology is similar to an extended star.
    • 20. 20 Mesh Topology A mesh topology is implemented to provide as much protection as possible from interruption of service. Each host has its own connections to all other hosts. Although the Internet has multiple paths to any one location, it does not adopt the full mesh topology.
    • 21. 21 LANs, MANs, & WANs One early solution was the creation of local-area network (LAN) standards which provided an open set of guidelines for creating network hardware and software, making equipment from different companies compatible. What was needed was a way for information to move efficiently and quickly, not only within a company, but also from one business to another. The solution was the creation of metropolitan-area networks (MANs) and wide-area networks (WANs).
    • 22. 22 Examples of Data Networks
    • 23. 23 LANs
    • 24. 24 Wireless LAN Organizations and Standards In cabled networks, IEEE is the prime issuer of standards for wireless networks. The standards have been created within the framework of the regulations created by the Federal Communications Commission (FCC). A key technology contained within the 802.11 standard is Direct Sequence Spread Spectrum (DSSS).
    • 25. 25 Cellular Topology for Wireless
    • 26. 26 WANs
    • 27. 27 SANs A SAN is a dedicated, high-performance network used to move data between servers and storage resources. Because it is a separate, dedicated network, it avoids any traffic conflict between clients and servers.
    • 28. 28 Virtual Private Network A VPN is a private network that is constructed within a public network infrastructure such as the global Internet. Using VPN, a telecommuter can access the network of the company headquarters through the Internet by building a secure tunnel between the telecommuter’s PC and a VPN router in the headquarters.
    • 29. 29 Bandwidth
    • 30. 30 Measuring Bandwidth
    • 31. 31
    • 32. 32 Why do we need the OSI Model? To address the problem of networks increasing in size and in number, the International Organization for Standardization (ISO) researched many network schemes and recognized that there was a need to create a network model that would help network builders implement networks that could communicate and work together and therefore, released the OSI reference model in 1984.
    • 33. 33 Don’t Get Confused. ISO - International Organization for Standardization OSI - Open System Interconnection IOS - Internetwork Operating System The ISO created the OSI to make the IOS more efficient. The “ISO” acronym is correct as shown. To avoid confusion, some people say “International Standard Organization.”
    • 34. 34 The OSI Reference Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical The OSI Model will be used throughout your entire networking career! Memorize it!
    • 35. 35 Layer 7 - The Application Layer 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer deal with networking applications. Examples: • Email • Web browsers PDU - User Data
    • 36. 36 Layer 6 - The Presentation Layer 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer is responsible for presenting the data in the required format which may include: • Encryption • Compression PDU - Formatted Data
    • 37. 37 Layer 5 - The Session Layer 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer establishes, manages, and terminates sessions between two communicating hosts. Example: • Client Software ( Used for logging in) PDU - Formatted Data
    • 38. 38 Layer 4 - The Transport Layer 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer breaks up the data from the sending host and then reassembles it in the receiver. It also is used to insure reliable data transport across the network. PDU - Segments
    • 39. 39 Layer 3 - The Network Layer 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical Sometimes referred to as the “Cisco Layer”. Makes “Best Path Determination” decisions based on logical addresses (usually IP addresses). PDU - Packets
    • 40. 40 Layer 2 - The Data Link Layer 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer provides reliable transit of data across a physical link. Makes decisions based on physical addresses (usually MAC addresses). PDU - Frames
    • 41. 41 Layer 1 - The Physical Layer 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This is the physical media through which the data, represented as electronic signals, is sent from the source host to the destination host. Examples: • CAT5 (what we have) • Coaxial (like cable TV) • Fiber optic PDU - Bits
    • 42. 42 OSI Model Analogy Application Layer - Source Host After riding your new bicycle a few times in NewYork, you decide that you want to give it to a friend who lives in Munich,Germany.
    • 43. 43 OSI Model Analogy Presentation Layer - Source Host Make sure you have the proper directions to disassemble and reassemble the bicycle.
    • 44. 44 OSI Model Analogy Session Layer - Source Host Call your friend and make sure you have his correct address.
    • 45. 45 OSI Model Analogy Transport Layer - Source Host Disassemble the bicycle and put different pieces in different boxes. The boxes are labeled “1 of 3”, “2 of 3”, and “3 of 3”.
    • 46. 46 OSI Model Analogy Network Layer - Source Host Put your friend's complete mailing address (and yours) on each box.Since the packages are too big for your mailbox (and since you don’t have enough stamps) you determine that you need to go to the post office.
    • 47. 47 OSI Model Analogy Data Link Layer – Source Host Jamshedpur post office takes possession of the boxes.
    • 48. 48 OSI Model Analogy Physical Layer - Media The boxes are flown from India to USA.
    • 49. 49 OSI Model Analogy Data Link Layer - Destination New York post office receives your boxes.
    • 50. 50 OSI Model Analogy Network Layer - Destination Upon examining the destination address, New York post office determines that your boxes should be delivered to your written home address.
    • 51. 51 OSI Model Analogy Transport Layer - Destination Your friend calls you and tells you he got all 3 boxes and he is having another friend named BOB reassemble the bicycle.
    • 52. 52 OSI Model Analogy Session Layer - Destination Your friend hangs up because he is done talking to you.
    • 53. 53 OSI Model Analogy Presentation Layer - Destination BOB is finished and “presents” the bicycle to your friend. Another way to say it is that your friend is finally getting him “present”.
    • 54. 54 OSI Model Analogy Application Layer - Destination Your friend enjoys riding his new bicycle in New York.
    • 55. 55 Host Layers 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical These layers only exist in the source and destination host computers.
    • 56. 56 Media Layers 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical These layers manage the information out in the LAN or WAN between the source and destination hosts.
    • 57. 57
    • 58. 58
    • 59. 59 Data Flow Through a Network
    • 60. 60
    • 61. 61 LAN Physical Layer Various symbols are used to represent media types. The function of media is to carry a flow of information through a LAN.Networking media are considered Layer 1, or physical layer, components of LANs. Each media has advantages and disadvantages. Some of the advantage or disadvantage comparisons concern: • Cable length • Cost • Ease of installation • Susceptibility to interference Coaxial cable, optical fiber, and even free space can carry network signals. However, the principal medium that will be studied is Category 5 unshielded twisted-pair cable (Cat 5 UTP)
    • 62. 62 Unshielded Twisted Pair (UTP) Cable
    • 63. 63 UTP Implementation EIA/TIA specifies an RJ-45 connector for UTP cable. The RJ-45 transparent end connector shows eight colored wires. Four of the wires carry the voltage and are considered “tip” (T1 through T4). The other four wires are grounded and are called “ring” (R1 through R4). The wires in the first pair in a cable or a connector are designated as T1 & R1
    • 64. 64 Connection Media The registered jack (RJ-45) connector and jack are the most common. In some cases the type of connector on a network interface card (NIC) does not match the media that it needs to connect to. The attachment unit interface (AUI) connector allows different media to connect when used with the appropriate transceiver. A transceiver is an adapter that converts one type of connection to another.
    • 65. 65 Ethernet Standards The Ethernet standard specifies that each of the pins on an RJ-45 connector have a particular purpose. A NIC transmits signals on pins 1 & 2, and it receives signals on pins 3 & 6.
    • 66. 66 Remember… A straight-thru cable has T568B on both ends. A crossover (or cross-connect) cable has T568B on one end and T568A on the other. A console cable had T568B on one end and reverse T568B on the other, which is why it is also called a rollover cable.
    • 67. 67 Straight-Thru or Crossover Use straight-through cables for the following cabling: • Switch to router • Switch to PC or server • Hub to PC or server Use crossover cables for the following cabling: • Switch to switch • Switch to hub • Hub to hub • Router to router • PC to PC • Router to PC
    • 68. 68 Sources of Noise on Copper Media Noise is any electrical energy on the transmission cable that makes it difficult for a receiver to interpret the data sent from the transmitter. TIA/EIA-568-B certification of a cable now requires testing for a variety of types of noise.Twisted-pair cable is designed to take advantage of the effects of crosstalk in order to minimize noise. In twisted-pair cable, a pair of wires is used to transmit one signal.The wire pair is twisted so that each wire experiences similar crosstalk. Because a noise signal on one wire will appear identically on the other wire, this noise be easily detected and filtered at receiver.Twisting one pair of wires in a cable also helps to reduce crosstalk of data or noise signals from adjacent wires.
    • 69. 69 Shielded Twisted Pair (STP) Cable
    • 70. 70 Coaxial Cable
    • 71. 71 Fiber Optic Cable
    • 72. 72 Fiber Optic Connectors Connectors are attached to the fiber ends so that the fibers can be connected to the ports on the transmitter and receiver. The type of connector most commonly used with multimode fiber is the Subscriber Connector (SC connector).On single-mode fiber, the Straight Tip (ST) connector is frequently used
    • 73. 73 Fiber Optic Patch Panels Fiber patch panels similar to the patch panels used with copper cable.
    • 74. 74 Cable Specifications 10BASE-T The T stands for twisted pair. 10BASE5 The 5 represents the fact that a signal can travel for approximately 500 meters 10BASE5 is often referred to as Thicknet. 10BASE2 The 2 represents the fact that a signal can travel for approximately 200 meters 10BASE2 is often referred to as Thinnet. All 3 of these specifications refer to the speed of transmission at 10 Mbps and a type of transmission that is baseband, or digitally interpreted. Thinnet and Thicknet are actually a type of networks, while 10BASE2 & 10BASE5 are the types of cabling
    • 75. 75 Ethernet Media Connector Requirements
    • 76. 76 LAN Physical Layer Implementation
    • 77. 77 Ethernet in the Campus
    • 78. 78 WAN Physical Layer
    • 79. 79 WAN Serial Connection Options
    • 80. 80 Serial Implementation of DTE & DCE When connecting directly to a service provider, or to a device such as a CSU/DSU that will perform signal clocking, the router is a DTE and needs a DTE serial cable. This is typically the case for routers.
    • 81. 81 Back-to-Back Serial Connection When performing a back-to-back router scenario in a test environment, one of the routers will be a DTE and the other will be a DCE.
    • 82. 82 Repeater A repeater is a network device used to regenerate a signal. Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuation.Repeater is a Physical Layer device
    • 83. 83 The 4 Repeater Rule The Four Repeater Rule for 10-Mbps Ethernet should be used as a standard when extending LAN segments. This rule states that no more than four repeaters can be used between hosts on a LAN. This rule is used to limit latency added to frame travel by each repeater.
    • 84. 84 Hub Hubs concentrate connections.In other words, they take a group of hosts and allow the network to see them as a single unit. Hub is a physical layer device.
    • 85. 85 Network Interface Card The function of a NIC is to connect a host device to the network medium. A NIC is a printed circuit board that fits into the expansion slot on the motherboard or peripheral device of a computer. The NIC is also referred to as a network adapter. NICs are considered Data Link Layer devices because each NIC carries a unique code called a MAC address.
    • 86. 86 MAC Address MAC address is 48 bits in length and expressed as twelve hexadecimal digits.MAC addresses are sometimes referred to as burned-in addresses (BIA) because they are burned into read-only memory (ROM) and are copied into random-access memory (RAM) when the NIC initializes.
    • 87. 87 Bridge Bridges are Data Link layer devices.Connected host addresses are learned and stored on a MAC address table.Each bridge port has a unique MAC address
    • 88. 88 Bridges
    • 89. 89 Bridging Graphic
    • 90. 90 Switch Switches are Data Link layer devices. Each Switch port has a unique MAC address. Connected host MAC addresses are learned and stored on a MAC address table.
    • 91. 91 Switching Modes cut-through A switch starts to transfer the frame as soon as the destination MAC address is received. No error checking is available. Must use synchronous switching. store-and-forward At the other extreme, the switch can receive the entire frame before sending it out the destination port. This gives the switch software an opportunity to verify the Frame Check Sum (FCS) to ensure that the frame was reliably received before sending it to the destination. Must be used with asynchronous switching. fragment-free A compromise between the cut-through and store-and-forward modes. Fragment-free reads the first 64 bytes, which includes the frame header, and switching begins before the entire data field and checksum are read.
    • 92. 92 Full Duplex Another capability emerges when only two nodes are connected. In a network that uses twisted-pair cabling, one pair is used to carry the transmitted signal from one node to the other node. A separate pair is used for the return or received signal. It is possible for signals to pass through both pairs simultaneously. The capability of communication in both directions at once is known as full duplex.
    • 93. 93 Switches – MAC Tables
    • 94. 94 Switches – Parallel Communication
    • 95. 95 Microsegmentation A switch is simply a bridge with many ports. When only one node is connected to a switch port, the collision domain on the shared media contains only two nodes. The two nodes in this small segment, or collision domain, consist of the switch port and the host connected to it. These small physical segments are called micro segments.
    • 96. 96 Peer-to-Peer Network In a peer-to-peer network, networked computers act as equal partners, or peers. As peers, each computer can take on the client function or the server function. At one time, computer A may make a request for a file from computer B, which responds by serving the file to computer A. Computer A functions as client, while B functions as the server. At a later time, computers A and B can reverse roles. In a peer-to-peer network, individual users control their own resources. Peer-to-peer networks are relatively easy to install and operate. As networks grow, peer-to-peer relationships become increasingly difficult to coordinate.
    • 97. 97 Client/Server Network In a client/server arrangement, network services are located on a dedicated computer called a server. The server responds to the requests of clients. The server is a central computer that is continuously available to respond to requests from clients for file, print, application, and other services. Most network operating systems adopt the form of a client/server relationship.
    • 98. 98
    • 99. 99 Why Another Model? Although the OSI reference model is universally recognized, the historical and technical open standard of the Internet is Transmission Control Protocol / Internet Protocol (TCP/IP). The TCP/IP reference model and the TCP/IP protocol stack make data communication possible between any two computers, anywhere in the world, at nearly the speed of light. The U.S. Department of Defense (DoD) created the TCP/IP reference model because it wanted a network that could survive any conditions, even a nuclear war.
    • 100. 100 Don’t Confuse the Models Application Transport Internet Network Access 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical
    • 101. 101 2 Models Side-By-Side Application Transport Internet Network Access 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical
    • 102. 102 The Application Layer The application layer of the TCP/IP model handles high- level protocols, issues of representation, encoding, and dialog control.
    • 103. 103 The transport layer provides transport services from the source host to the destination host. It constitutes a logical connection between these endpoints of the network. Transport protocols segment and reassemble upper-layer applications into the same data stream between endpoints. The transport layer data stream provides end- to-end transport services. The Transport Layer
    • 104. 104 The Internet Layer The purpose of the Internet layer is to select the best path through the network for packets to travel. The main protocol that functions at this layer is the Internet Protocol (IP). Best path determination and packet switching occur at this layer.
    • 105. 105 The Network Access Layer The network access layer is also called the host-to-network layer. It the layer that is concerned with all of the issues that an IP packet requires to actually make a physical link to the network media. It includes LAN and WAN details, and all the details contained in the OSI physical and data-link layers. NOTE: ARP & RARP work at both the Internet and Network Access Layers.
    • 106. 106 Comparing TCP/IP & OSI Models NOTE: TCP/IP transport layer using UDP does not always guarantee reliable delivery of packets as the transport layer in the OSI model does.
    • 107. 107 Introduction to the Transport Layer The primary duties of the transport layer, Layer 4 of the OSI model, are to transport and regulate the flow of information from the source to the destination, reliably and accurately. End-to-end control and reliability are provided by sliding windows, sequencing numbers, and acknowledgments.
    • 108. 108 More on The Transport Layer The transport layer provides transport services from the source host to the destination host. It establishes a logical connection between the endpoints of the network. • Transport services include the following basic services: • Segmentation of upper-layer application data • Establishment of end-to-end operations • Transport of segments from one end host to another end host • Flow control provided by sliding windows • Reliability provided by sequence numbers and acknowledgments
    • 109. 109 Flow Control As the transport layer sends data segments, it tries to ensure that data is not lost. A receiving host that is unable to process data as quickly as it arrives could be a cause of data loss. Flow control avoids the problem of a transmitting host overflowing the buffers in the receiving host.
    • 110. 110 3-Way Handshake TCP requires connection establishment before data transfer begins. For a connection to be established or initialized, the two hosts must synchronize their Initial Sequence Numbers (ISNs).
    • 111. 111 Basic Windowing Data packets must be delivered to the recipient in the same order in which they were transmitted to have a reliable, connection-oriented data transfer. The protocol fails if any data packets are lost, damaged, duplicated, or received in a different order. An easy solution is to have a recipient acknowledge the receipt of each packet before the next packet is sent.
    • 112. 112 Sliding Window
    • 113. 113 Sliding Window with Different Window Sizes
    • 114. 114 TCP Sequence & Acknowledgement
    • 115. 115 TCP Transmission Control Protocol (TCP) is a connection-oriented Layer 4 protocol that provides reliable full-duplex data transmission. TCP is part of the TCP/IP protocol stack. In a connection-oriented environment, a connection is established between both ends before the transfer of information can begin. TCP is responsible for breaking messages into segments, reassembling them at the destination station, resending anything that is not received, and reassembling messages from the segments.TCP supplies a virtual circuit between end-user applications. The protocols that use TCP include: • FTP (File Transfer Protocol) • HTTP (Hypertext Transfer Protocol) • SMTP (Simple Mail Transfer Protocol) • Telnet
    • 116. 116 TCP Segment Format
    • 117. 117 UDP User Datagram Protocol (UDP) is the connectionless transport protocol in the TCP/IP protocol stack. UDP is a simple protocol that exchanges datagrams, without acknowledgments or guaranteed delivery. Error processing and retransmission must be handled by higher layer protocols. UDP uses no windowing or acknowledgments so reliability, if needed, is provided by application layer protocols. UDP is designed for applications that do not need to put sequences of segments together. The protocols that use UDP include: • TFTP (Trivial File Transfer Protocol) • SNMP (Simple Network Management Protocol) • DHCP (Dynamic Host Control Protocol) • DNS (Domain Name System)
    • 118. 118 UDP Segment Format
    • 119. 119 Well Known Port Numbers The following port numbers should be memorized: NOTE: The curriculum forgot to mention one of the most important port numbers. Port 80 is used for HTTP or WWW protocols. (Essentially access to the internet.)
    • 120. 120 URL
    • 121. 121 SNMP – Managed Network
    • 122. 122
    • 123. 123 Base 2 Number System 101102 = (1 x 24 = 16) + (0 x 23 = 0) + (1 x 22 = 4) + (1 x 21 = 2) + (0 x 20 = 0) = 22
    • 124. 124 Converting Decimal to Binary Convert 20110 to binary: 201 / 2 = 100 remainder 1 100 / 2 = 50 remainder 0 50 / 2 = 25 remainder 0 25 / 2 = 12 remainder 1 12 / 2 = 6 remainder 0 6 / 2 = 3 remainder 0 3 / 2 = 1 remainder 1 1 / 2 = 0 remainder 1 When the quotient is 0, take all the remainders in reverse order for your answer: 20110 = 110010012
    • 125. 125
    • 126. 126 Network and Host Addressing Using the IP address of the destination network, a router can deliver a packet to the correct network. When the packet arrives at a router connected to the destination network, the router uses the IP address to locate the particular computer connected to that network. Accordingly, every IP address has two parts.
    • 127. 127 Network Layer Communication Path A router forwards packets from the originating network to the destination network using the IP protocol. The packets must include an identifier for both the source and destination networks.
    • 128. 128 Internet Addresses IP Addressing is a hierarchical structure.An IP address combines two identifiers into one number. This number must be a unique number, because duplicate addresses would make routing impossible.The first part identifies the system's network address.The second part, called the host part, identifies which particular machine it is on the network.
    • 129. 129 IP Address Classes IP addresses are divided into classes to define the large, medium, and small networks. Class A addresses are assigned to larger networks. Class B addresses are used for medium-sized networks, & Class C for small networks.
    • 130. 130 Identifying Address Classes
    • 131. 131 Address Class Prefixes To accommodate different size networks and aid in classifying these networks, IP addresses are divided into groups called classes.This is classful addressing.
    • 132. 132 Network and Host Division Each complete 32-bit IP address is broken down into a network part and a host part. A bit or bit sequence at the start of each address determines the class of the address. There are 5 IP address classes.
    • 133. 133 Class A Addresses The Class A address was designed to support extremely large networks, with more than 16 million host addresses available. Class A IP addresses use only the first octet to indicate the network address. The remaining three octets provide for host addresses.
    • 134. 134 Class B Addresses The Class B address was designed to support the needs of moderate to large-sized networks.A Class B IP address uses the first two of the four octets to indicate the network address. The other two octets specify host addresses.
    • 135. 135 Class C Addresses The Class C address space is the most commonly used of the original address classes.This address space was intended to support small networks with a maximum of 254 hosts.
    • 136. 136 Class D Addresses The Class D address class was created to enable multicasting in an IP address. A multicast address is a unique network address that directs packets with that destination address to predefined groups of IP addresses. Therefore, a single station can simultaneously transmit a single stream of data to multiple recipients.
    • 137. 137 Class E Addresses A Class E address has been defined. However, the Internet Engineering Task Force (IETF) reserves these addresses for its own research. Therefore, no Class E addresses have been released for use in the Internet.
    • 138. 138 IP Address Ranges The graphic below shows the IP address range of the first octet both in decimal and binary for each IP address class.
    • 139. 139 IPv4 As early as 1992, the Internet Engineering Task Force (IETF) identified two specific concerns: Exhaustion of the remaining, unassigned IPv4 network addresses and the increase in the size of Internet routing tables. Over the past two decades, numerous extensions to IPv4 have been developed. Two of the more important of these are subnet masks and classless interdomain routing (CIDR).
    • 140. 140 Finding the Network Address with ANDing By ANDing the Host address of 192.168.10.2 with 255.255.255.0 (its network mask) we obtain the network address of 192.168.10.0
    • 141. 141 Network Address
    • 142. 142 Broadcast Address
    • 143. 143 Network/Broadcast Addresses at the Binary Level An IP address that has binary 0s in all host bit positions is reserved for the network address, which identifies the network. An IP address that has binary 1s in all host bit positions is reserved for the broadcast address, which is used to send data to all hosts on the network. Here are some examples: Class Network Address Broadcast Address A 100.0.0.0 100.255.255.255 B 150.75.0.0 150.75.255.255 C 200.100.50.0 200.100.50.255
    • 144. 144 Public IP Addresses Unique addresses are required for each device on a network.  Originally, an organization known as the Internet Network Information Center (InterNIC) handled this procedure. InterNIC no longer exists and has been succeeded by the Internet Assigned Numbers Authority (IANA). No two machines that connect to a public network can have the same IP address because public IP addresses are global and standardized. All machines connected to the Internet agree to conform to the system. Public IP addresses must be obtained from an Internet service provider (ISP) or a registry at some expense.
    • 145. 145 Private IP Addresses Private IP addresses are another solution to the problem of the impending exhaustion of public IP addresses.As mentioned, public networks require hosts to have unique IP addresses. However, private networks that are not connected to the Internet may use any host addresses, as long as each host within the private network is unique.
    • 146. 146 Mixing Public and Private IP Addresses Private IP addresses can be intermixed, as shown in the graphic, with public IP addresses.This will conserve the number of addresses used for internal connections. Connecting a network using private addresses to the Internet requires translation of the private addresses to public addresses. This translation process is referred to as Network Address Translation (NAT).
    • 147. 147 Introduction to Subnetting Subnetting a network means to use the subnet mask to divide the network and break a large network up into smaller, more efficient and manageable segments, or subnets. With subnetting, the network is not limited to the default Class A, B, or C network masks and there is more flexibility in the network design. Subnet addresses include the network portion, plus a subnet field and a host field. The ability to decide how to divide the original host portion into the new subnet and host fields provides addressing flexibility for the network administrator.
    • 148. 148 The 32-Bit Binary IP Address
    • 149. 149 Numbers That Show Up In Subnet Masks (Memorize Them!)
    • 150. 150 Addressing with Subnetworks
    • 151. 151 Obtaining an Internet Address
    • 152. 152 Static Assignment of an IP Address Static assignment works best on small networks. The administrator manually assigns and tracks IP addresses for each computer, printer, or server on the intranet. Network printers, application servers, and routers should be assigned static IP addresses.
    • 153. 153 SIEMENS NI XDORF SIEMENS NIXDORF Host A Host B IP Address: 128.0.10.4 HW Address: 080020021545 ARP Reply ARP Request - Broadcast to all hosts „What is the hardware address for IP address 128.0.10.4?“ SI EMENS NI XDORF Fig. 32 How does ARP work? (TI1332EU02TI_0004 The Network Layer, 47) ARP (Address Resolution Protocol)
    • 154. 154 Fig. 33 The ARP command (TI1332EU02TI_0004 The Network Layer, 47)
    • 155. 155 B 1 Network = 1 Broadcast Domain Broadcast: ARP requestBroadcast: ARP request A B 2 Networks = 2 Broadcast Domains Broadcast: ARP requestBroadcast: ARP request A Router host B would reply no one would reply Fig. 34 Proxy-ARP concept (TI1332EU02TI_0004 The Network Layer, 49)
    • 156. 156 A Router R Broadcast Message to all: If your IP address matches “B” then please tell me your Ethernet address B A B Yes, I know the destination network, let me give you my Ethernet address I take care, to forward IP packets to B
    • 157. 157 RARP Reverse Address Resolution Protocol (RARP) associates a known MAC addresses with an IP addresses. A network device, such as a diskless workstation, might know its MAC address but not its IP address. RARP allows the device to make a request to learn its IP address. Devices using RARP require that a RARP server be present on the network to answer RARP requests.
    • 158. 158 BootP The bootstrap protocol (BOOTP) operates in a client-server environment and only requires a single packet exchange to obtain IP information. However, unlike RARP, BOOTP packets can include the IP address, as well as the address of a router, the address of a server, and vendor-specific information. One problem with BOOTP, however, is that it was not designed to provide dynamic address assignment. With BOOTP, a network administrator creates a configuration file that specifies the parameters for each device.The administrator must add hosts and maintain the BOOTP database. Even though the addresses are dynamically assigned, there is still a one to one relationship between the number of IP addresses and the number of hosts. This means that for every host on the network there must be a BOOTP profile with an IP address assignment in it. No two profiles can have the same IP address.
    • 159. 159 DHCP Dynamic host configuration protocol (DHCP) is the successor to BOOTP. Unlike BOOTP, DHCP allows a host to obtain an IP address dynamically without the network administrator having to set up an individual profile for each device. All that is required when using DHCP is a defined range of IP addresses on a DHCP server.As hosts come online, they contact the DHCP server and request an address. The DHCP server chooses an address and leases it to that host. With DHCP, the entire network configuration of a computer can be obtained in one message. This includes all of the data supplied by the BOOTP message, plus a leased IP address and a subnet mask. The major advantage that DHCP has over BOOTP is that it allows users to be mobile.
    • 160. 160
    • 161. 161 Introduction to Routers A router is a special type of computer. It has the same basic components as a standard desktop PC. However, routers are designed to perform some very specific functions. Just as computers need operating systems to run software applications, routers need the Internetwork Operating System software (IOS) to run configuration files. These configuration files contain the instructions and parameters that control the flow of traffic in and out of the routers. The many parts of a router are shown below:
    • 162. 162 RAM Random Access Memory, also called dynamic RAM (DRAM) RAM has the following characteristics and functions: • Stores routing tables • Holds ARP cache • Holds fast-switching cache • Performs packet buffering (shared RAM) • Maintains packet-hold queues • Provides temporary memory for the configuration file of the router while the router is powered on • Loses content when router is powered down or restarted
    • 163. 163 NVRAM Non-Volatile RAM NVRAM has the following characteristics and functions: • Provides storage for the startup configuration file • Retains content when router is powered down or restarted
    • 164. 164 Flash Flash memory has the following characteristics and functions: • Holds the operating system image (IOS) • Allows software to be updated without removing and replacing chips on the processor • Retains content when router is powered down or restarted • Can store multiple versions of IOS software Is a type of electronically erasable, programmable ROM (EEPROM)
    • 165. 165 ROM Read-Only Memory ROM has the following characteristics and functions: • Maintains instructions for power-on self test (POST) diagnostics • Stores bootstrap program and basic operating system software • Requires replacing pluggable chips on the motherboard for software upgrades
    • 166. 166 Interfaces Interfaces have the following characteristics and functions: • Connect router to network for frame entry and exit • Can be on the motherboard or on a separate module Types of interfaces: • Ethernet • Fast Ethernet • Serial • Token ring • ISDN BRI • Loopback • Console • Aux
    • 167. 167 Internal Components of a 2600 Router
    • 168. 168 External Components of a 2600 Router
    • 169. 169 External Connections
    • 170. 170 Fixed Interfaces When cabling routers for serial connectivity, the routers will either have fixed or modular ports. The type of port being used will affect the syntax used later to configure each interface. Interfaces on routers with fixed serial ports are labeled for port type and port number.
    • 171. 171 Modular Serial Port Interfaces Interfaces on routers with modular serial ports are labeled for port type, slot, and port number.The slot is the location of the module.To configure a port on a modular card, it is necessary to specify the interface using the syntax “port type slot number/port number.” Use the label “serial 0/1,” when the interface is serial, the slot number where the module is installed is slot 0, and the port that is being referenced is port 1.
    • 172. 172 Routers & DSL Connections The Cisco 827 ADSL router has one asymmetric digital subscriber line (ADSL) interface. To connect a router for DSL service, use a phone cable with RJ-11 connectors. DSL works over standard telephone lines using pins 3 and 4 on a standard RJ-11 connector.
    • 173. 173 Computer/Terminal Console Connection
    • 174. 174 Modem Connection to Console/Aux Port
    • 175. 175 HyperTerminal Session Properties
    • 176. 176 Establishing a HyperTerminal Session Take the following steps to connect a terminal to the console port on the router: First, connect the terminal using the RJ-45 to RJ-45 rollover cable and an RJ-45 to DB-9 or RJ-45 to DB-25 adapter. Then, configure the terminal or PC terminal emulation software for 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control.
    • 177. 177 Cisco IOS Cisco technology is built around the Cisco Internetwork Operating System (IOS), which is the software that controls the routing and switching functions of internetworking devices. A solid understanding of the IOS is essential for a network administrator.
    • 178. 178 The Purpose of Cisco IOS As with a computer, a router or switch cannot function without an operating system. Cisco calls its operating system the Cisco Internetwork Operating System or Cisco IOS. It is the embedded software architecture in all of the Cisco routers and is also the operating system of the Catalyst switches. Without an operating system, the hardware does not have any capabilities. The Cisco IOS provides the following network services: • Basic routing and switching functions • Reliable and secure access to networked resources • Network scalability
    • 179. 179 Router Command Line Interface
    • 180. 180 Setup Mode Setup is not intended as the mode for entering complex protocol features in the router. The purpose of the setup mode is to permit the administrator to install a minimal configuration for a router, unable to locate a configuration from another source.  In the setup mode, default answers appear in square brackets [ ] following the question. Press the Enter key to use these defaults. During the setup process, Ctrl-C can be pressed at any time to terminate the process. When setup is terminated using Ctrl-C, all interfaces will be administratively shutdown. When the configuration process is completed in setup mode, the following options will be displayed: [0] Go to the IOS command prompt without saving this config. [1] Return back to the setup without saving this config. [2] Save this configuration to nvram and exit. Enter your selection [2]:
    • 181. 181 Operation of Cisco IOS Software The Cisco IOS devices have three distinct operating environments or modes: • ROM monitor • Boot ROM • Cisco IOS The startup process of the router normally loads into RAM and executes one of these operating environments. The configuration register setting can be used by the system administrator to control the default start up mode for the router. To see the IOS image and version that is running, use the show version command, which also indicates the configuration register setting.
    • 182. 182 IOS File System Overview
    • 183. 183 Initial Startup of Cisco Routers A router initializes by loading the bootstrap, the operating system, and a configuration file. If the router cannot find a configuration file, it enters setup mode. Upon completion of the setup mode a backup copy of the configuration file may be saved to nonvolatile RAM (NVRAM). The goal of the startup routines for Cisco IOS software is to start the router operations. To do this, the startup routines must accomplish the following: • Make sure that the router hardware is tested and functional. • Find and load the Cisco IOS software. • Find and apply the startup configuration file or enter the setup mode. When a Cisco router powers up, it performs a power-on self test (POST). During this self test, the router executes diagnostics from ROM on all hardware modules.
    • 184. 184 After the Post… After the POST, the following events occur as the router initializes: Step 1 The generic bootstrap loader in ROM executes. A bootstrap is a simple set of instructions that tests hardware and initializes the IOS for operation.  Step 2 The IOS can be found in several places. The boot field of the configuration register determines the location to be used in loading the IOS. If the boot field indicates a flash or network load, boot system commands in the configuration file indicate the exact name and location of the image. Step 3 The operating system image is loaded. Step 4 The configuration file saved in NVRAM is loaded into main memory and executed one line at a time. The configuration commands start routing processes, supply addresses for interfaces, and define other operating characteristics of the router. Step 5 If no valid configuration file exists in NVRAM, the operating system searches for an available TFTP server. If no TFTP server is found, the setup dialog is initiated.  
    • 185. 185 Step in Router Initialization
    • 186. 186 Router LED Indicators Cisco routers use LED indicators to provide status information. Depending upon the Cisco router model, the LED indicators will vary. An interface LED indicates the activity of the corresponding interface. If an LED is off when the interface is active and the interface is correctly connected, a problem may be indicated. If an interface is extremely busy, its LED will always be on. The green OK LED to the right of the AUX port will be on after the system initializes correctly.
    • 187. 187 Enhanced Cisco IOS Commands
    • 188. 188 The show version Command The show version command displays information about the Cisco IOS software version that is currently running on the router. This includes the configuration register and the boot field settings. The following information is available from the show version command: IOS version and descriptive information • Bootstrap ROM version • Boot ROM version • Router up time • Last restart method • System image file and location • Router platform • Configuration register setting Use the show version command to identify router IOS image and boot source. To find out the amount of flash memory, issue the show flash command.
    • 189. 189
    • 190. 190
    • 191. 191 Router User Interface Modes The Cisco command-line interface (CLI) uses a hierarchical structure. This structure requires entry into different modes to accomplish particular tasks. Each configuration mode is indicated with a distinctive prompt and allows only commands that are appropriate for that mode. As a security feature the Cisco IOS software separates sessions into two access levels, user EXEC mode and privileged EXEC mode. The privileged EXEC mode is also known as enable mode.
    • 192. 192 Overview of Router Modes
    • 193. 193 Router Modes
    • 194. 194 User Mode Commands
    • 195. 195 Privileged Mode Commands NOTE: There are many more commands available in privileged mode.
    • 196. 196 Specific Configuration Modes
    • 197. 197 CLI Command Modes All command-line interface (CLI) configuration changes to a Cisco router are made from the global configuration mode. Other more specific modes are entered depending upon the configuration change that is required. Global configuration mode commands are used in a router to apply configuration statements that affect the system as a whole. The following command moves the router into global configuration mode Router#configure terminal (or config t) Router(config)# When specific configuration modes are entered, the router prompt changes to indicate the current configuration mode. Typing exit from one of these specific configuration modes will return the router to global configuration mode. Pressing Ctrl-Z returns the router to all the way back privileged EXEC mode.
    • 198. 198 Configuring a Router’s Name A router should be given a unique name as one of the first configuration tasks. This task is accomplished in global configuration mode using the following commands: Router(config)#hostname Tokyo Tokyo(config)# As soon as the Enter key is pressed, the prompt changes from the default host name (Router) to the newly configured host name (which is Tokyo in the example above).
    • 199. 199 Setting the Clock with Help
    • 200. 200 Message Of The Day (MOTD) A message-of-the-day (MOTD) banner can be displayed on all connected terminals. Enter global configuration mode by using the command config t Enter the command banner motd # The message of the day goes here #. Save changes by issuing the command copy run start
    • 201. 201 Configuring a Console Password Passwords restrict access to routers. Passwords should always be configured for virtual terminal lines and the console line. Passwords are also used to control access to privileged EXEC mode so that only authorized users may make changes to the configuration file. The following commands are used to set an optional but recommended password on the console line: Router(config)#line console 0 Router(config-line)#password <password> Router(config-line)#login
    • 202. 202 Configuring a Modem Password If configuring a router via a modem you are most likely connected to the aux port. The method for configuring the aux port is very similar to configuring the console port. Router(config)#line aux 0 Router(config-line)#password <password> Router(config-line)#login
    • 203. 203 Configuring Interfaces An interface needs an IP Address and a Subnet Mask to be configured. All interfaces are “shutdown” by default. The DCE end of a serial interface needs a clock rate. Router#config t Router(config)#interface serial 0/1 Router(config-if)#ip address 200.100.50.75 255.255.255.240 Router(config-if)#clock rate 56000 (required for serial DCE only) Router(config-if)#no shutdown Router(config-if)#exit Router(config)#int f0/0 Router(config-if)#ip address 150.100.50.25 255.255.255.0 Router(config-if)#no shutdown Router(config-if)#exit Router(config)#exit Router# On older routers, Serial 0/1 would be just Serial 1 and f0/0 would be e0. s = serial e = Ethernet f = fast Ethernet
    • 204. 204 Configuring a Telnet Password A password must be set on one or more of the virtual terminal (VTY) lines for users to gain remote access to the router using Telnet. Typically Cisco routers support five VTY lines numbered 0 through 4. The following commands are used to set the same password on all of the VTY lines: Router(config)#line vty 0 4 Router(config-line)#password <password> Router(config-line)#login
    • 205. 205 Examining the show Commands There are many show commands that can be used to examine the contents of files in the router and for troubleshooting. In both privileged EXEC and user EXEC modes, the command show ? provides a list of available show commands. The list is considerably longer in privileged EXEC mode than it is in user EXEC mode. show interfaces – Displays all the statistics for all the interfaces on the router. show int s0/1 – Displays statistics for interface Serial 0/1 show controllers serial – Displays information-specific to the interface hardware show clock – Shows the time set in the router show hosts – Displays a cached list of host names and addresses show users – Displays all users who are connected to the router show history – Displays a history of commands that have been entered show flash – Displays info about flash memory and what IOS files are stored there show version – Displays info about the router and the IOS that is running in RAM show ARP – Displays the ARP table of the router show start – Displays the saved configuration located in NVRAM show run – Displays the configuration currently running in RAM show protocol – Displays the global and interface specific status of any configured Layer 3 protocols
    • 206. 206
    • 207. 207
    • 208. 208
    • 209. 209 Ethernet Overview Ethernet is now the dominant LAN technology in the world. Ethernet is not one technology but a family of LAN technologies. All LANs must deal with the basic issue of how individual stations (nodes) are named, and Ethernet is no exception. Ethernet specifications support different media, bandwidths, and other Layer 1 and 2 variations. However, the basic frame format and addressing scheme is the same for all varieties of Ethernet.
    • 210. 210 Ethernet and the OSI Model Ethernet operates in two areas of the OSI model, the lower half of the data link layer, known as the MAC sublayer and the physical layer
    • 211. 211 Ethernet Technologies Mapped to the OSI Model
    • 212. 212 Layer 2 Framing Framing is the Layer 2 encapsulation process. A frame is the Layer 2 protocol data unit. The frame format diagram shows different groupings of bits (fields) that perform other functions.
    • 213. 213 Ethernet and IEEE Frame Formats are Very Similar
    • 214. 214 3 Common Layer 2 Technologies Ethernet Uses CSMA/CD logical bus topology (information flow is on a linear bus) physical star or extended star (wired as a star) Token Ring logical ring topology (information flow is controlled in a ring) and a physical star topology (in other words, it is wired as a star) FDDI logical ring topology (information flow is controlled in a ring) and physical dual- ring topology(wired as a dual- ring)
    • 215. 215 Collision Domains To move data between one Ethernet station and another, the data often passes through a repeater. All other stations in the same collision domain see traffic that passes through a repeater. A collision domain is then a shared resource. Problems originating in one part of the collision domain will usually impact the entire collision domain.
    • 216. 216 CSMA/CD Graphic
    • 217. 217 Backoff After a collision occurs and all stations allow the cable to become idle (each waits the full interframe spacing), then the stations that collided must wait an additional and potentially progressively longer period of time before attempting to retransmit the collided frame. The waiting period is intentionally designed to be random so that two stations do not delay for the same amount of time before retransmitting, which would result in more collisions.
    • 218. 218
    • 219. Hierarchical Addressing Using Variable-Length Subnet Masks © 2003, Cisco Systems, Inc. All rights reserved. 219
    • 220. 220 Prefix Length and Network Mask Range of Addresses: 192.168.1.64 through 192.168.1.79 • Have the first 28 bits in common, which is represented by a /28 prefix length • 28 bits in common can also be represented in dotted decimal as 255.255.255.240 In the IP network number that accompanies the network mask, when the host bits of the IP network number are: • All binary zeros – that address is the bottom of the address range • All binary ones – that address is the top of the address range Binary ones in the network mask represent network bits in the accompanying IP address; binary zeros represent host bits 11000000.10101000.00000001.0100xxxx IP Address 11111111.11111111.11111111.11110000 Network Mask Fourth Octet 64 01000000 65 01000001 66 01000010 67 01000011 68 01000100 69 01000101 70 01000110 71 01000111 72 01001000 73 01001001 74 01001010 75 01001011 76 01001100 77 01001101 78 01001110 79 01001111
    • 221. 221 Implementing VLSM
    • 222. 222 Range Of Addresses for VLSM
    • 223. 223 Breakdown Address Space for Largest Subnet
    • 224. 224 for Ethernets at Remote Sites
    • 225. 225 Address Space for Serial Subnets
    • 226. 226 Calculating VLSM: Binary
    • 227. Route Summarization and Classless Interdomain Routing © 2003, Cisco Systems, Inc. All rights reserved. 227
    • 228. 228 What Is Route Summarization?
    • 229. 229 Summarizing Within an Octet
    • 230. 230 Summarizing Addresses in a VLSM-Designed Network
    • 231. 231 Classless Interdomain Routing –CIDR is a mechanism developed to alleviate exhaustion of addresses and reduce routing table size. –Block addresses can be summarized into single entries without regard to the classful boundary of the network number. –Summarized blocks are installed in routing tables.
    • 232. 232 What Is CIDR? • Addresses are the same as in the route summarization figure, except that Class B network 172 has been replaced by Class C network 192.
    • 233. 233 CIDR Example
    • 234. 234
    • 235. 235 Anatomy of an IP Packet IP packets consist of the data from upper layers plus an IP header. The IP header consists of the following:
    • 236. 236
    • 237. 237
    • 238. 238
    • 239. 239 Administrative Distance The administrative distance is an optional parameter that gives a measure of the reliability of the route. The range of an AD is 0-255 where smaller numbers are more desireable. The default administrative distance when using next-hop address is 1, while the default administrative distance when using the outgoing interface is 0. You can statically assign an AD as follows: Router(config)#ip route 172.16.3.0 255.255.255.0 172.16.4.1 130 Sometimes static routes are used for backup purposes. A static route can be configured on a router that will only be used when the dynamically learned route has failed. To use a static route in this manner, simply set the administrative distance higher than that of the dynamic routing protocol being used.
    • 240. 240 Configuring Default Routes Default routes are used to route packets with destinations that do not match any of the other routes in the routing table. A default route is actually a special static route that uses this format: ip route 0.0.0.0 0.0.0.0 [next-hop-address | outgoing interface] This is sometimes referred to as a “Quad-Zero” route. Example using next hop address: Router(config)#ip route 0.0.0.0 0.0.0.0 172.16.4.1 Example using the exit interface: Router(config)#ip route 0.0.0.0 0.0.0.0 s0/0
    • 241. 241 Verifying Static Route Configuration After static routes are configured it is important to verify that they are present in the routing table and that routing is working as expected. The command show running-config is used to view the active configuration in RAM to verify that the static route was entered correctly. The show ip route command is used to make sure that the static route is present in the routing table.
    • 242. 242
    • 243. 243 Path Determination Graphic
    • 244. 244 Router Router Router Router Router What is an optimal route ? What is an optimal route ? Switch Switch Routing Protocol
    • 245. 245 Routing Protocols Routing protocols includes the following: processes for sharing route information allows routers to communicate with other routers to update and maintain the routing tables Examples of routing protocols that support the IP routed protocol are: RIP, IGRP, OSPF, BGP, and EIGRP.
    • 246. 246
    • 247. 247 Routed Protocols Protocols used at the network layer that transfer data from one host to another across a router are called routed or routable protocols. The Internet Protocol (IP) and Novell's Internetwork Packet Exchange (IPX) are examples of routed protocols. Routers use routing protocols to exchange routing tables and share routing information. In other words, routing protocols enable routers to route routed protocols.
    • 248. 248
    • 249. 249 Autonomous System AS 2000 AS 3000 IGP Interior Gateway Protocols are used for routing decisions within an Autonomous System. Exterior Gateway Protocols are used for routing between Autonomous Systems EGP AS 1000 An Autonomous System (AS) is a group of IP networks, which has a single and clearly defined external routing policy. Fig. 48 IGP and EGP (TI1332EU02TI_0004 The Network Layer, 67)
    • 250. 250 IGP Interior Gateway Protocol (IGP) Exterior Gateway Protocol (EGP) EGP EGP EGP Interior Gateway Protocol (IGP) AS 1000 AS 2000 AS 3000 Fig. 49 The use of IGP and EGP protocols (TI1332EU02TI_0004 The Network Layer, 67)
    • 251. 251 IGP and EGP An autonomous system is a network or set of networks under common administrative control, such as the cisco.com domain.
    • 252. 252 Categories of Routing Protocols Most routing algorithms can be classified into one of two categories: • distance vector • link-state The distance vector routing approach determines the direction (vector) and distance to any link in the internetwork. The link-state approach, also called shortest path first, recreates the exact topology of the entire internetwork.
    • 253. 253 Distance Vector Routing Concepts
    • 254. 254 2 Hops 1 Hop1 Hop Destination 192.16.1.0 192.16.5.0 192.16.7.0 Distance 1 1 2 Routing table contains the addresses of destinations and the distance of the way to this destination. Flow of routing information Flow of routing information Router B Router CRouter A Router D 192.16.1.0192.16.1.0 192.16.7.0192.16.7.0 192.16.5.0192.16.5.0 Distance Vector Routing (DVR)
    • 255. 255 Routing Tables Graphic
    • 256. 256 Distance Vector Topology Changes
    • 257. 257 Router Metric Components
    • 258. 258 Router CRouter A Router D 192.16.1.0192.16.1.0 192.16.7.0192.16.7.0 192.16.5.0192.16.5.0 Router B 192.16.3.0192.16.3.0 192.16.2.0192.16.2.0 192.16.4.0192.16.4.0 192.16.6.0192.16.6.0 192.16.1.0192.16.1.0 192.16.2.0192.16.2.0 192.16.4.0192.16.4.0 192.16.5.0192.16.5.0 192.16.6.0192.16.6.0 192.16.6.0192.16.6.0 192.16.7.0192.16.7.0 192.16.2.0192.16.2.0 192.16.3.0192.16.3.0 192.16.4.0192.16.4.0 192.16.4.0192.16.4.0 192.16.5.0192.16.5.0 192.16.6.0192.16.6.0 192.16.6.0192.16.6.0 192.16.7.0192.16.7.0 192.16.1.0192.16.1.0 192.16.2.0192.16.2.0 192.16.2.0192.16.2.0 192.16.3.0192.16.3.0 192.16.4.0192.16.4.0192.16.3.0192.16.3.0 192.16.4.0192.16.4.0 192.16.1.0192.16.1.0 192.16.5.0192.16.5.0 192.16.6.0192.16.6.0 192.16.3.0192.16.3.0 192.16.2.0192.16.2.0 192.16.7.0192.16.7.0 192.16.5.0192.16.5.0 192.16.4.0192.16.4.0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 11 11 11 11 11 11 11 11 LL LL LL LL LL LL LL LL LL LL LL LL LL LL LL LL LL LL 11 11 00 00 LL LL BB BB AA CC CC BB BB DD CC CC LL Locally connectedLocally connected Distance Vector Routing (DVR)
    • 259. 259 192.16.4.0192.16.4.0 192.16.5.0192.16.5.0 192.16.6.0192.16.6.0 192.16.6.0192.16.6.0 192.16.7.0192.16.7.0 192.16.1.0192.16.1.0 192.16.2.0192.16.2.0 192.16.2.0192.16.2.0 192.16.3.0192.16.3.0 192.16.4.0192.16.4.0192.16.3.0192.16.3.0 192.16.4.0192.16.4.0 192.16.1.0192.16.1.0 192.16.5.0192.16.5.0 192.16.6.0192.16.6.0 192.16.3.0192.16.3.0 192.16.2.0192.16.2.0 192.16.7.0192.16.7.0 192.16.5.0192.16.5.0 192.16.4.0192.16.4.0 192.16.5.0192.16.5.0 192.16.6.0192.16.6.0 192.16.7.0192.16.7.0 192.16.1.0192.16.1.0 192.16.3.0192.16.3.0 192.16.2.0192.16.2.0 00 00 00 00 00 00 00 00 00 00 11 11 11 11 11 11 11 11 11 11 22 22 22 22 22 22 LL LL LL LL LL LL LL LL LL LL BB BB AA CC CC BB BB DD CC CC BB BB CC BB CC CC 192.16.4.0192.16.4.0 192.16.5.0192.16.5.0 192.16.6.0192.16.6.0 192.16.6.0192.16.6.0 192.16.7.0192.16.7.0 192.16.1.0192.16.1.0 192.16.2.0192.16.2.0 192.16.2.0192.16.2.0 192.16.3.0192.16.3.0 192.16.4.0192.16.4.0192.16.3.0192.16.3.0 192.16.4.0192.16.4.0 192.16.1.0192.16.1.0 192.16.5.0192.16.5.0 192.16.6.0192.16.6.0 192.16.3.0192.16.3.0 192.16.2.0192.16.2.0 192.16.7.0192.16.7.0 192.16.5.0192.16.5.0 192.16.4.0192.16.4.0 192.16.5.0192.16.5.0 192.16.6.0192.16.6.0 192.16.7.0192.16.7.0 192.16.1.0192.16.1.0 192.16.3.0192.16.3.0 192.16.2.0192.16.2.0 192.16.1.0192.16.1.0192.16.7.0192.16.7.0 00 00 00 00 00 00 00 00 00 00 11 11 11 11 11 11 11 11 11 11 22 22 22 22 22 22 3333 LL LL LL LL LL LL LL LL LL LL BB BB AA CC CC BB BB DD CC CC BB BB CC BB CC CC BB CC Distance Vector Routing (DVR) Fig. 53 Distribution of routing information with distance vector routing protocol (cont.) (TI1332EU02TI_0004 The Network Layer, 71)
    • 260. 260 RIPv1 Distance Vector Routing Protocol, classful Distribution of Routing Tables via broadcast to adjacent routers Only one kind of metric: Number of Hops Connections with different bandwidth can not be weighted Routing loops can occur -> bad convergence in case of a failure Count to infinity problem (infinity = 16) Maximum network size is limited by the number of hops Fig.59PropertiesofRIPv1(TI1332EU02TI_0004TheNetworkLayer,81)
    • 261. 261 RIP Characteristics
    • 262. 262 200.14.13.0/24200.14.13.0/24 130.24.13.0/24130.24.13.0/24 Router A Port 2 200.14.13.2/24 Port 2 200.14.13.2/24 Port 1 130.24.13.1/24 Port 1 130.24.13.1/24 130.24.36.0/24130.24.36.0/24 RIP-1: 130.24.36.0 RIP-1: 130.24.36.0 RIP-1: 130.24.0.0 130.24.25.0/24130.24.25.0/24 RIP-1 permits only a Single Subnet Mask Fig. 60 RIP-1 permits only a single subnet mask (TI1332EU02TI_0004 The Network Layer, 83)
    • 263. 263 Router Configuration The router command starts a routing process. The network command is required because it enables the routing process to determine which interfaces participate in the sending and receiving of routing updates. An example of a routing configuration is: GAD(config)#router rip GAD(config-router)#network 172.16.0.0 The network numbers are based on the network class addresses, not subnet addresses or individual host addresses.
    • 264. 264 Configuring RIP Example
    • 265. 265 Verifying RIP Configuration
    • 266. 266 The debug ip rip Command Most of the RIP configuration errors involve an incorrect network statement, discontiguous subnets, or split horizons. One highly effective command for finding RIP update issues is the debug ip rip command. The debug ip rip command displays RIP routing updates as they are sent and received.
    • 267. 267 Problem: Routing LoopsRouting loops can occur when inconsistent routing tables are not updated due to slow convergence in a changing network.
    • 268. 268 Problem: Counting to Infinity
    • 269. 269 Solution: Define a Maximum
    • 270. 270 Solution: Split Horizon
    • 271. 271 Route Poisoning Route poisoning is used by various distance vector protocols in order to overcome large routing loops and offer explicit information when a subnet or network is not accessible. This is usually accomplished by setting the hop count to one more than the maximum.
    • 272. 272 Triggered Updates New routing tables are sent to neighboring routers on a regular basis. For example, RIP updates occur every 30 seconds. However a triggered update is sent immediately in response to some change in the routing table. The router that detects a topology change immediately sends an update message to adjacent routers that, in turn, generate triggered updates notifying their adjacent neighbors of the change. When a route fails, an update is sent immediately rather than waiting on the update timer to expire. Triggered updates, used in conjunction with route poisoning, ensure that all routers know of failed routes before any holddown timers can expire.
    • 273. 273 Triggered Updates Graphic
    • 274. 274 Solution: Holddown Timers
    • 275. 275 IGRP Interior Gateway Routing Protocol (IGRP) is a proprietary protocol developed by Cisco. Some of the IGRP key design characteristics emphasize the following: • It is a distance vector routing protocol. • Routing updates are broadcast every 90 seconds. • Bandwidth, load, delay and reliability are used to create a composite metric.
    • 276. 276 IGRP Stability Features IGRP has a number of features that are designed to enhance its stability, such as: • Holddowns • Split horizons • Poison reverse updates Holddowns Holddowns are used to prevent regular update messages from inappropriately reinstating a route that may not be up. Split horizons Split horizons are derived from the premise that it is usually not useful to send information about a route back in the direction from which it came. Poison reverse updates Split horizons prevent routing loops between adjacent routers, but poison reverse updates are necessary to defeat larger routing loops. Today, IGRP is showing its age, it lacks support for variable length subnet masks (VLSM). Rather than develop an IGRP version 2 to correct this problem, Cisco has built upon IGRP's legacy of success with Enhanced IGRP.
    • 277. 277 Configuring IGRP
    • 278. 278 Routing Metrics Graphics
    • 279. 279 Link State Concepts
    • 280. 280 Link State Topology Changes
    • 281. 281 LSP: „My links to R2 and R4 are up“ LSP: „My links to R1 and R3 are up, my link to R4 is down.“ LSP: „My links to R2 and R4 are up.“ LSP: „My links to R1 and R3 are up. My link to R2 is down.“ Router 1 Router 4 Router 2 Router 3 SPF Routing Table Link State Routing (LSR) LSP....link state packet SPF... shortest path first
    • 282. 282 Link State Concerns
    • 283. 283 Router A Router C Router B Router D Router E22 11 44 22 44 11 B - 2 C - 1 B - 2 C - 1 A - 2 D - 4 A - 2 D - 4 A - 1 D - 2 E - 4 A - 1 D - 2 E - 4 C - 2 B - 4 E - 1 C - 2 B - 4 E - 1 C - 4 D - 1 C - 4 D - 1 Router A Router B Router C Router D Router E Link State Database AA CB D E A D EC BB D A E B CC E C B A DD Link State Routing (LSR)
    • 284. 284 Link State Routing Features Link-state algorithms are also known as Dijkstras algorithm or as SPF (shortest path first) algorithms. Link-state routing algorithms maintain a complex database of topology information. The distance vector algorithm are also known as Bellman-Ford algorithms. They have nonspecific information about distant networks and no knowledge of distant routers. A link-state routing algorithm maintains full knowledge of distant routers and how they interconnect. Link-state routing uses: • Link-state advertisements (LSAs) A link-state advertisement (LSA) is a small packet of routing information that is sent between routers. • Topological database A topological database is a collection of information gathered from LSAs. • SPF algorithm The shortest path first (SPF) algorithm is a calculation performed on the database resulting in the SPF tree. • Routing tables – A list of the known paths and interfaces.
    • 285. 285 Link State Routing
    • 286. 286 Comparing Routing Methods
    • 287. OSPF (Open Shortest Path First) Protocol © 2003, Cisco Systems, Inc. All rights reserved. 287
    • 288. 288 OSPF is a Link-State Routing Protocols –Link-state (LS) routers recognize much more information about the network than their distance-vector counterparts,Consequently LS routers tend to make more accurate decisions. –Link-state routers keep track of the following: • Their neighbours • All routers within the same area • Best paths toward a destination
    • 289. 289 Link-State Data Structures –Neighbor table: • Also known as the adjacency database (list of recognized neighbors) –Topology table: • Typically referred to as LSDB (routers and links in the area or network) • All routers within an area have an identical LSDB –Routing table: • Commonly named a forwarding database (list of best paths to destinations)
    • 290. 290 OSPF vs. RIP RIP is limited to 15 hops, it converges slowly, and it sometimes chooses slow routes because it ignores critical factors such as bandwidth in route determination. OSPF overcomes these limitations and proves to be a robust and scalable routing protocol suitable for the networks of today.
    • 291. 291 OSPF Terminology The next several slides explain various OSPF terms -one per slide.
    • 292. 292 OSPF Term: Link
    • 293. 293 OSPF Term: Link State
    • 294. 294 OSPF Term: Area
    • 295. 295 OSPF Term: Link Cost
    • 296. 296 OSPF Term: Forwarding Database
    • 297. 297 OSPF Term: Adjacencies Database
    • 298. 298 OSPF Terms: DR & BDR
    • 299. 299 Link-State Data Structure: Network Hierarchy •Link-state routing requires a hierachical network structure that is enforced by OSPF. •This two-level hierarchy consists of the following: • Transit area (backbone or area 0) • Regular areas (nonbackbone areas)
    • 300. 300 OSPF Areas
    • 301. 301 Area Terminology
    • 302. 302 LS Data Structures: Adjacency Database – Routers discover neighbors by exchanging hello packets. – Routers declare neighbors to be up after checking certain parameters or options in the hello packet. – Point-to-point WAN links: • Both neighbors become fully adjacent. – LAN links: • Neighbors form an adjacency with the DR and BDR. • Maintain two-way state with the other routers (DROTHERs). – Routing updates and topology information are only passed between adjacent routers.
    • 303. 303 OSPF Adjacencies Routers build logical adjacencies between each other using the Hello Protocol. Once an adjacency is formed: • LS database packets are exchanged to synchronize each other’s LS databases. • LSAs are flooded reliably throughout the area or network using these adjacencies.
    • 304. 304
    • 305. 305 Open Shortest Path First Calculation •Routers find the best paths to destinations by applying Dijkstra’s SPF algorithm to the link- state database as follows: – Every router in an area has the identical link-state database. – Each router in the area places itself into the root of the tree that is built. – The best path is calculated with respect to the lowest total cost of links to a specific destination. – Best routes are put into the forwarding database.
    • 306. 306 OSPF Packet Types
    • 307. 307 OSPF Packet Header Format
    • 308. 308 Neighborship
    • 309. 309 Establishing Bidirectional Communication
    • 310. 310 Establishing Bidirectional Communication (Cont.)
    • 311. 311 Establishing Bidirectional Communication (Cont.)
    • 312. 312 Establishing Bidirectional Communication
    • 313. 313 Discovering the Network Routes
    • 314. 314 Discovering the Network Routes
    • 315. 315 Adding the Link-State Entries
    • 316. 316 Adding the Link-State Entries (Cont.)
    • 317. 317 Adding the Link-State Entries
    • 318. 318 Maintaining Routing Information • Router A notifies all OSPF DRs on 224.0.0.6
    • 319. 319 Maintaining Routing Information (Cont.) • Router A notifies all OSPF DRs on 224.0.0.6 • DR notifies others on 224.0.0.5
    • 320. 320 Maintaining Routing Information (Cont.) • Router A notifies all OSPF DRs on 224.0.0.6 • DR notifies others on 224.0.0.5
    • 321. 321 Maintaining Routing Information • Router A notifies all OSPF DRs on 224.0.0.6 • DR notifies others on 224.0.0.5
    • 322. 322 router ospf process-idrouter ospf process-id Router(config)# •Turns on one or more OSPF routing processes in the IOS software. Configuring Basic OSPF: Single Area network address inverse-mask area [area-id]network address inverse-mask area [area-id] Router(config-router)# •Router OSPF subordinate command that defines the interfaces (by network number) that OSPF will run on. Each network number must be defined to a specific area.
    • 323. 323 Configuring OSPF on Internal Routers of a Single Area
    • 324. 324 show ip protocolsshow ip protocols Router# • Verifies the configured IP routing protocol processes, parameters and statistics Verifying OSPF Operation show ip route ospfshow ip route ospf Router# •Displays all OSPF routes learned by the router show ip ospf interfaceshow ip ospf interface Router# •Displays the OSPF router ID, area ID and adjacency information
    • 325. 325 show ip ospfshow ip ospf Router# •Displays the OSPF router ID, timers, and statistics Verifying OSPF Operation (Cont.) show ip ospf neighbor [detail]show ip ospf neighbor [detail] Router# •Displays information about the OSPF neighbors, including Designated Router (DR) and Backup Designated Router (BDR) information on broadcast networks
    • 326. 326 The show ip route ospf Command RouterA# show ip route ospf Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP, D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area, E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP, i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default Gateway of last resort is not set 10.0.0.0 255.255.255.0 is subnetted, 2 subnets O 10.2.1.0 [110/10] via 10.64.0.2, 00:00:50, Ethernet0
    • 327. 327 The show ip ospf interface Command RouterA# show ip ospf interface e0 Ethernet0 is up, line protocol is up Internet Address 10.64.0.1/24, Area 0 Process ID 1, Router ID 10.64.0.1, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State DROTHER, Priority 1 Designated Router (ID) 10.64.0.2, Interface address 10.64.0.2 Backup Designated router (ID) 10.64.0.1, Interface address 10.64.0.1 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:04 Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 10.64.0.2 (Designated Router) Suppress hello for 0 neighbor(s)
    • 328. 328 The show ip ospf neighbor Command RouterB# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.64.1.1 1 FULL/BDR 00:00:31 10.64.1.1 Ethernet0 10.2.1.1 1 FULL/- 00:00:38 10.2.1.1 Serial0
    • 329. 329 show ip protocol show ip route
    • 330. 330 show ip ospf neighbor detail show ip ospf database
    • 331. 331 OSPF Network Types - 1
    • 332. 332 Point-to-Point Links • Usually a serial interface running either PPP or HDLC • May also be a point-to-point subinterface running Frame Relay or ATM • No DR or BDR election required • OSPF autodetects this interface type • OSPF packets are sent using multicast 224.0.0.5
    • 333. 333 Multi-access Broadcast Network • Generally LAN technologies like Ethernet and Token Ring • DR and BDR selection required • All neighbor routers form full adjacencies with the DR and BDR only • Packets to the DR use 224.0.0.6 • Packets from DR to all other routers use 224.0.0.5
    • 334. 334 Electing the DR and BDR • Hello packets are exchanged via IP multicast. • The router with the highest OSPF priority is selected as the DR. • Use the OSPF router ID as the tie breaker. • The DR election is nonpreemptive.
    • 335. 335 Setting Priority for DR Election ip ospf priority numberip ospf priority number •This interface configuration command assigns the OSPF priority to an interface. •Different interfaces on a router may be assigned different values. •The default priority is 1. The range is from 0 to 255. •0 means the router is a DROTHER; it can’t be the DR or BDR. Router(config-if)#
    • 336. 336 OSPF Network Types - 2
    • 337. 337 Creation of Adjacencies RouterA# debug ip ospf adj Point-to-point interfaces coming up: No election %LINK-3-UPDOWN: Interface Serial1, changed state to up OSPF: Interface Serial1 going Up OSPF: Rcv hello from 192.168.0.11 area 0 from Serial1 10.1.1.2 OSPF: End of hello processing OSPF: Build router LSA for area 0, router ID 192.168.0.10 OSPF: Rcv DBD from 192.168.0.11 on Serial1 seq 0x20C4 opt 0x2 flag 0x7 len 32 state INIT OSPF: 2 Way Communication to 192.168.0.11 on Serial1, state 2WAY OSPF: Send DBD to 192.168.0.11 on Serial1 seq 0x167F opt 0x2 flag 0x7 len 32 OSPF: NBR Negotiation Done. We are the SLAVE OSPF: Send DBD to 192.168.0.11 on Serial1 seq 0x20C4 opt 0x2 flag 0x2 len 72
    • 338. 338 Creation of Adjacencies (Cont.) RouterA# debug ip ospf adj Ethernet interface coming up: Election OSPF: 2 Way Communication to 192.168.0.10 on Ethernet0, state 2WAY OSPF: end of Wait on interface Ethernet0 OSPF: DR/BDR election on Ethernet0 OSPF: Elect BDR 192.168.0.12 OSPF: Elect DR 192.168.0.12 DR: 192.168.0.12 (Id) BDR: 192.168.0.12 (Id) OSPF: Send DBD to 192.168.0.12 on Ethernet0 seq 0x546 opt 0x2 flag 0x7 len 32 <…> OSPF: DR/BDR election on Ethernet0 OSPF: Elect BDR 192.168.0.11 OSPF: Elect DR 192.168.0.12 DR: 192.168.0.12 (Id) BDR: 192.168.0.11 (Id)
    • 339. 339
    • 340. 340 Overview Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco- proprietary routing protocol based on Interior Gateway Routing Protocol (IGRP). Unlike IGRP, which is a classful routing protocol, EIGRP supports CIDR and VLSM. Compared to IGRP, EIGRP boasts faster convergence times, improved scalability, and superior handling of routing loops. Furthermore, EIGRP can replace Novell Routing Information Protocol (RIP) and AppleTalk Routing Table Maintenance Protocol (RTMP), serving both IPX and AppleTalk networks with powerful efficiency. EIGRP is often described as a hybrid routing protocol, offering the best of distance vector and link-state algorithms.
    • 341. 341 Comparing EIGRP with IGRP IGRP and EIGRP are compatible with each other. EIGRP offers multiprotocol support, but IGRP does not. EIGRP and IGRP use different metric calculations. EIGRP scales the metric of IGRP by a factor of 256. IGRP has a maximum hop count of 255. EIGRP has a maximum hop count limit of 224. Enabling dissimilar routing protocols such as OSPF and RIP to share information requires advanced configuration. Redistribution, the sharing of routes, is automatic between IGRP and EIGRP as long as both processes use the same autonomous system (AS) number.
    • 342. 342 EIGRP & IGRP Metric Calculation
    • 343. 343 Comparing EIGRP with IGRP
    • 344. 344 Comparing EIGRP with IGRP
    • 345. 345 EIGRP Concepts & Terminology EIGRP routers keep route and topology information readily available in RAM, so they can react quickly to changes. Like OSPF, EIGRP saves this information in several tables and databases. EIGRP saves routes that are learned in specific ways. Routes are given a particular status and can be tagged to provide additional useful information. EIGRP maintains three tables: • Neighbor table • Topology table • Routing table
    • 346. 346 Neighbor Table The neighbor table is the most important table in EIGRP. Each EIGRP router maintains a neighbor table that lists adjacent routers. This table is comparable to the adjacency database used by OSPF. There is a neighbor table for each protocol that EIGRP supports. When a neighbor sends a hello packet, it advertises a hold time. The hold time is the amount of time a router treats a neighbor as reachable and operational. In other words, if a hello packet is not heard within the hold time, then the hold time expires. When the hold time expires, the Diffusing Update Algorithm (DUAL), which is the EIGRP distance vector algorithm, is informed of the topology change and must recalculate the new topology.
    • 347. 347 Topology Table The topology table is made up of all the EIGRP routing tables in the autonomous system. DUAL takes the information supplied in the neighbor table and the topology table and calculates the lowest cost routes to each destination. By tracking this information, EIGRP routers can identify and switch to alternate routes quickly. The information that the router learns from the DUAL is used to determine the successor route, which is the term used to identify the primary or best route. A copy is also placed in the topology table. Every EIGRP router maintains a topology table for each configured network protocol. All learned routes to a destination are maintained in the topology table.
    • 348. 348 Routing Table The EIGRP routing table holds the best routes to a destination. This information is retrieved from the topology table. Each EIGRP router maintains a routing table for each network protocol. A successor is a route selected as the primary route to use to reach a destination.DUAL identifies this route from the information contained in the neighbor and topology tables and places it in the routing table. There can be up to four successor routes for any particular route. These can be of equal or unequal cost and are identified as the best loop-free paths to a given destination. A copy of the successor routes is also placed in the topology table. A feasible successor (FS) is a backup route.These routes are identified at the same time the successors are identified, but they are only kept in the topology table. Multiple feasible successors for a destination can be retained in the topology table although it is not mandatory.
    • 349. 349 EIGRP Data Structure Like OSPF, EIGRP relies on different types of packets to maintain its various tables and establish complex relationships with neighbor routers. The five EIGRP packet types are: • Hello • Acknowledgment • Update • Query • Reply EIGRP relies on hello packets to discover, verify, and rediscover neighbor routers. Rediscovery occurs if EIGRP routers do not receive hellos from each other for a hold time interval but then re-establish communication. EIGRP routers send hellos at a fixed but configurable interval, called the hello interval. The default hello interval depends on the bandwidth of the interface. On IP networks, EIGRP routers send hellos to the multicast IP address 224.0.0.10.
    • 350. 350 Default Hello Intervals and Hold Times for EIGRP
    • 351. 351 EIGRP Algorithm The sophisticated DUAL algorithm results in the exceptionally fast convergence of EIGRP. Each router constructs a topology table that contains information about how to route to a destination network. Each topology table identifies the following: • The routing protocol or EIGRP • The lowest cost of the route, which is called Feasible Distance • The cost of the route as advertised by the neighboring router, which is called Reported Distance The Topology heading identifies the preferred primary route, called the successor route (Successor), and, where identified, the backup route, called the feasible successor (FS). Note that it is not necessary to have an identified feasible successor.
    • 352. 352 FS Route Selection Rules
    • 353. 353 DUAL Example
    • 354. 354 Configuring EIGRP
    • 355. 355
    • 356. 356
    • 357. 357
    • 358. 358 Verifying the EIGRP Configuration To verify the EIGRP configuration a number of show and debug commands are available. These commands are shown on the next few slides.
    • 359. 359
    • 360. 360 show ip eigrp topology show ip eigrp topology [active | pending | successors]
    • 361. 361 show ip eigrp topology all-links show ip eigrp traffic
    • 362. 362 Administrative Distances
    • 363. 363 Classful and Classless Routing Protocols
    • 364. 364
    • 365. 365 What are ACLs? ACLs are lists of conditions that are applied to traffic traveling across a router's interface.  These lists tell the router what types of packets to accept or deny. Acceptance and denial can be based on specified conditions. ACLs can be created for all routed network protocols, such as Internet Protocol (IP) and Internetwork Packet Exchange (IPX). ACLs can be configured at the router to control access to a network or subnet. Some ACL decision points are source and destination addresses, protocols, and upper-layer port numbers. ACLs must be defined on a per-protocol, per direction, or per port basis.
    • 366. 366 Reasons to Create ACLs The following are some of the primary reasons to create ACLs: • Limit network traffic and increase network performance. • Provide traffic flow control. • Provide a basic level of security for network access. • Decide which types of traffic are forwarded or blocked at the router interfaces. For example: Permit e-mail traffic to be routed, but block all telnet traffic. Allow an administrator to control what areas a client can access on a network. If ACLs are not configured on the router, all packets passing through the router will be allowed onto all parts of the network.
    • 367. 367 ACLs Filter Traffic Graphic
    • 368. 368 How ACLs Filter Traffic
    • 369. 369 One List per Port, per Destination, per Protocol...
    • 370. 370 How ACLs work.
    • 371. 371 Creating ACLs ACLs are created in the global configuration mode. There are many different types of ACLs including standard, extended, IPX, AppleTalk, and others. When configuring ACLs on a router, each ACL must be uniquely identified by assigning a number to it. This number identifies the type of access list created and must fall within the specific range of numbers that is valid for that type of list. Since IP is by far the most popular routed protocol, addition ACL numbers have been added to newer router IOSs. Standard IP: 1300-1999 Extended IP: 2000-2699
    • 372. 372 The access-list command
    • 373. 373 The ip access-group command { in | out }
    • 374. 374 ACL Example
    • 375. 375 Basic Rules for ACLs These basic rules should be followed when creating and applying access lists: • One access list per protocol per direction. • Standard IP access lists should be applied closest to the destination. • Extended IP access lists should be applied closest to the source. • Use the inbound or outbound interface reference as if looking at the port from inside the router. • Statements are processed sequentially from the top of list to the bottom until a match is found, if no match is found then the packet is denied. • There is an implicit deny at the end of all access lists. This will not appear in the configuration listing. • Access list entries should filter in the order from specific to general. Specific hosts should be denied first, and groups or general filters should come last. • Never work with an access list that is actively applied. • New lines are always added to the end of the access list. • A no access-list x command will remove the whole list. It is not possible to selectively add and remove lines with numbered ACLs. • Outbound filters do not affect traffic originating from the local router.
    • 376. 376 Wildcard Mask Examples 5 Examples follow that demonstrate how a wildcard mask can be used to permit or deny certain IP addresses, or IP address ranges. While subnet masks start with binary 1s and end with binary 0s, wildcard masks are the reverse meaning they typically start with binary 0s and end with binary 1s. In the examples that follow Cisco has chosen to represent the binary 1s in the wilcard masks with Xs to focus on the specific bits being shown in each example. You will see that while subnet masks were ANDed with ip addresses, wildcard masks are ORed with IP addresses. .
    • 377. 377 Wildcard Mask Example #1
    • 378. 378 Wildcard Mask Example #2
    • 379. 379 Wildcard Mask Example #3
    • 380. 380 Wildcard Mask Example #4 - Even IPs
    • 381. 381 Wildcard Mask Example #5 - Odd IP#s
    • 382. 382 The any and host Keywords
    • 383. 383 Verifying ACLs There are many show commands that will verify the content and placement of ACLs on the router. The show ip interface command displays IP interface information and indicates whether any ACLs are set. The show access-lists command displays the contents of all ACLs on the router. show access-list 1 shows just access-list 1. The show running-config command will also reveal the access lists on a router and the interface assignment information.
    • 384. 384 Standard ACLs Standard ACLs check the source address of IP packets that are routed. The comparison will result in either permit or deny access for an entire protocol suite, based on the network, subnet, and host addresses. The standard version of the access-list global configuration command is used to define a standard ACL with a number in the range of 1 to 99 (also from 1300 to 1999 in recent IOS). If there is no wildcard mask. the default mask is used, which is 0.0.0.0. (This only works with Standard ACLs and is the same thing as using host.) The full syntax of the standard ACL command is: Router(config)#access-list access-list-number {deny | permit} source [source-wildcard ] [log] The no form of this command is used to remove a standard ACL. This is the syntax: Router(config)#no access-list access-list-number
    • 385. 385 Extended ACLs Extended ACLs are used more often than standard ACLs because they provide a greater range of control. Extended ACLs check the source and destination packet addresses as well as being able to check for protocols and port numbers. The syntax for the extended ACL statement can get very long and often will wrap in the terminal window. The wildcards also have the option of using the host or any keywords in the command. At the end of the extended ACL statement, additional precision is gained from a field that specifies the optional Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) port number. Logical operations may be specified such as, equal (eq), not equal (neq), greater than (gt), and less than (lt), that the extended ACL will perform on specific protocols. Extended ACLs use an access-list-number in the range 100 to 199 (also from 2000 to 2699 in recent IOS).
    • 386. 386 Extended ACL Syntax
    • 387. 387
    • 388. 388 Extended ACL Example This extended ACL will allow people in network 200.100.50.0 to surfing the internet, but not allow any other protocols like email, ftp, etc. access-list 101 permit tcp 200.100.50.0 0.0.0.255 any eq 80 or access-list 101 permit tcp 200.100.50.0 0.0.0.255 any eq www or access-list 101 permit tcp 200.100.50.0 0.0.0.255 any eq http NOTE: Just like all Standard ACLs end with an implicit "deny any", all Extended ACLs end with an implicit "deny ip any any" which means deny the entire internet from anywhere to anywhere.
    • 389. 389 ip access-group The ip access-group command links an existing standard or extended ACL to an interface. Remember that only one ACL per interface, per direction, per protocol is allowed. The format of the command is: Router(config-if)#ip access-group access-list- number {in | out}
    • 390. 390 Named ACLs IP named ACLs were introduced in Cisco IOS Software Release 11.2, allowing standard and extended ACLs to be given names instead of numbers. The advantages that a named access list provides are: • Intuitively identify an ACL using an alphanumeric name. • Eliminate the limit of 798 simple and 799 extended ACLs • Named ACLs provide the ability to modify ACLs without deleting them completely and then reconfiguring them. Named ACLs are not compatible with Cisco IOS releases prior to Release 11.2. The same name may not be used for multiple ACLs.
    • 391. 391 Named ACL Example
    • 392. 392 Placing ACLs The general rule is to put the extended ACLs as close as possible to the source of the traffic denied. Standard ACLs do not specify destination addresses, so they should be placed as close to the destination as possible. For example, in the graphic a standard ACL should be placed on Fa0/0 of Router D to prevent traffic from Router A.
    • 393. 393
    • 394. 394 Permitting a Single Host Router(config)# access-list 1 permit 200.100.50.23 0.0.0.0 or Router(config)# access-list 1 permit host 200.100.50.23 or Router(config)# access-list 1 permit 200.100.50.23 (The implicit “deny any” ensures that everyone else is denied.) Router(config)# int e0 Router(config-if)# ip access-group 1 in or Router(config-if)# ip access-group 1 out
    • 395. 395 Denying a Single Host Router(config)# access-list 1 deny 200.100.50.23 0.0.0.0 Router(config)# access-list 1 permit 0.0.0.0 255.255.255.255 or Router(config)# access-list 1 deny host 200.100.50.23 Router(config)# access-list 1 permit any (The implicit “deny any” is still present, but totally irrelevant.) Router(config)# int e0 Router(config-if)# ip access-group 1 in or Router(config-if)# ip access-group 1 out
    • 396. 396 Permitting a Single Network Class C Router(config)# access-list 1 permit 200.100.50.0 0.0.0.255 or Class B Router(config)# access-list 1 permit 150.75.0.0 0.0.255.255 or Class A Router(config)# access-list 1 permit 13.0.0.0 0.255.255.255 (The implicit “deny any” ensures that everyone else is denied.) Router(config)# int e0 Router(config-if)# ip access-group 1 in or Router(config-if)# ip access-group 1 out
    • 397. 397 Denying a Single Network Class C Router(config)# access-list 1 deny 200.100.50.0 0.0.0.255 Router(config)# access-list 1 permit any or Class B Router(config)# access-list 1 deny 150.75.0.0 0.0.255.255 Router(config)# access-list 1 permit any or Class A Router(config)# access-list 1 deny 13.0.0.0 0.255.255.255 Router(config)# access-list 1 permit any (The implicit “deny any” is still present, but totally irrelevant.)
    • 398. 398 Permitting a Class C Subnet Network Address/Subnet Mask: 200.100.50.0/28 Desired Subnet: 3rd Process: 32-28=4 2^4 = 16 1st Usable Subnet address range it 200.100.50.16-31 2nd Usable Subnet address range it 200.100.50.32-47 3rd Usable Subnet address range it 200.100.50.48-63 Subnet Mask is 255.255.255.240 Inverse Mask is 0.0.0.15 or subtract 200.100.50.48 from 200.100.50.63 to get 0.0.0.15 Router(config)# access-list 1 permit 200.100.50.48 0.0.0.15 (The implicit “deny any” ensures that everyone else is denied.)
    • 399. 399 Denying a Class C Subnet Network Address/Subnet Mask: 192.68.72.0/27 Undesired Subnet: 2nd Process: 32-27=5 2^5=32 1st Usable Subnet address range it 192.68.72.32-63 2nd Usable Subnet address range it 192.68.72.64-95 Subnet Mask is 255.255.255.224 Inverse Mask is 0.0.0.31 or subtract 192.68.72.64 from 192.68.72.95 to get 0.0.0.31 Router(config)# access-list 1 deny 192.68.72.64 0.0.0.31 Router(config)# access-list 1 permit any (The implicit “deny any” is still present, but totally irrelevant.)
    • 400. 400 Permitting a Class B Subnet Network Address/Subnet Mask: 150.75.0.0/24 Desired Subnet: 129th Process: Since exactly 8 bits are borrowed the 3rd octet will denote the subnet number. 129th Usable Subnet address range it 150.75.129.0-255 Subnet Mask is 255.255.255.0 Inverse Mask is 0.0.0.255 or subtract 150.75.129.0 from 150.75.129.255 to get 0.0.0.255 Router(config)# access-list 1 permit 150.75.129.0 0.0.0.255 (The implicit “deny any” ensures that everyone else is denied.)
    • 401. 401 Denying a Class B Subnet Network Address/Subnet Mask: 160.88.0.0/22 Undesired Subnet: 50th Process: 32-22=10 (more than 1 octet) 10-8=2 2^2=4 1st Usable Subnet address range it 160.88.4.0-160.88.7.255 2nd Usable Subnet address range it 160.88.8.0-160.88.11.255 50 * 4 = 200 50th subnet is 160.88.200.0-160.88.203.255 Subnet Mask is 255.255.252.0 Inverse Mask is 0.0.3.255 or subtract 160.88.200.0 from 160.88.203.255 to get 0.0.3.255 Router(config)# access-list 1 deny 160.88.200.0 0.0.3.255 Router(config)# access-list 1 permit any
    • 402. 402 Permitting a Class A Subnet Network Address/Subnet Mask: 111.0.0.0/12 Desired Subnet: 13th Process: 32-12=20 20-16=4 2^4=16 1st Usable Subnet address range is 111.16.0.0-111.31.255.255 13*16=208 13th Usable Subnet address range is 111.208.0.0-111.223.255.255 Subnet Mask is 255.240.0.0 Inverse Mask is 0.15.255.255 or subtract 111.208.0.0 from 111.223.255.255 to get 0.15.255.255 Router(config)# access-list 1 permit 111.208.0.0 0.15.255.255 (The implicit “deny any” ensures that everyone else is denied.)
    • 403. 403 Denying a Class A Subnet Network Address/Subnet Mask: 40.0.0.0/24 Undesired Subnet: 500th Process: Since exactly 16 bits were borrowed the 2nd and 3rd octet will denote the subnet. 1st Usable Subnet address range is 40.0.1.0-40.0.1.255 255th Usable Subnet address range is 40.0.255.0-40.0.255.255 256th Usable Subnet address range is 40.1.0.0-40.1.0.255 300th Usable Subnet address range is 40.1.44.0-40.1.44.255 500th Usable Subnet address range is 40.1.244.0-40.1.244.255 Router(config)# access-list 1 deny 40.1.244.0 0 0.0.0.255 Router(config)# access-list 1 permit any
    • 404. 404
    • 405. 405 Permit 200.100.50.24-100 Plan A access-list 1 permit host 200.100.50.24 access-list 1 permit host 200.100.50.25 access-list 1 permit host 200.100.50.26 access-list 1 permit host 200.100.50.27 access-list 1 permit host 200.100.50.28 : : : : : : : : access-list 1 permit host 200.100.50.96 access-list 1 permit host 200.100.50.97 access-list 1 permit host 200.100.50.98 access-list 1 permit host 200.100.50.99 access-list 1 permit host 200.100.50.100 This would get very tedious!
    • 406. 406 Permit 200.100.50.24-100 Plan B access-list 1 permit 200.100.50.24 0.0.0.7 (24-31) access-list 1 permit 200.100.50.32 0.0.0.31 (32-63) access-list 1 permit 200.100.50.64 0.0.0.31 (64-95) access-list 1 permit 200.100.50.96 0.0.0.3 (96-99) access-list 1 permit host 200.100.50.100 (100) (The implicit “deny any” ensures that everyone else is denied.)
    • 407. 407 Permit 200.100.50.16-127 Plan A access-list 1 permit 200.100.50.16 0.0.0.15 (16-31) access-list 1 permit 200.100.50.32 0.0.0.31 (32-63) access-list 1 permit 200.100.50.64 0.0.0.63 (64-127) (The implicit “deny any” ensures that everyone else is denied.)
    • 408. 408 Permit 200.100.50.16-127 Plan B access-list 1 deny 200.100.50.0 0.0.0.15 (0-15) access-list 1 permit 200.100.50.0 0.0.0.127 (0-127) First we make sure that addresses 0-15 are denied. Then we can permit any address in the range 0-127. Since only the first matching statement in an ACL is applied an address in the range of 0-15 will be denied by the first statement before it has a chance to be permitted by the second. (The implicit “deny any” ensures that everyone else is
    • 409. 409 Permit 200.100.50.1,5,13,29,42,77 access-list 1 permit host 200.100.50.1 access-list 1 permit host 200.100.50.5 access-list 1 permit host 200.100.50.13 access-list 1 permit host 200.100.50.29 access-list 1 permit host 200.100.50.42 access-list 1 permit host 200.100.50.77 Sometimes a group of addresses has no pattern and the best way to deal with them is individually. (The implicit “deny any” ensures that everyone else is
    • 410. 410
    • 411. 411 Permit Source Network access-list 101 permit ip 200.100.50.0 0.0.0.255 0.0.0.0 255.255.255.255 or access-list 101 permit ip 200.100.50.0 0.0.0.255 any Implicit deny ip any any
    • 412. 412 Deny Source Network access-list 101 deny ip 200.100.50.0 0.0.0.255 0.0.0.0 255.255.255.255 access-list 101 permit ip 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255 or access-list 101 deny ip 200.100.50.0 0.0.0.255 any access-list 101 permit ip any any Implicit deny ip any any is present but irrelevant.
    • 413. 413 Permit Destination Network access-list 101 permit ip 0.0.0.0 255.255.255.255 200.100.50.0 0.0.0.255 or access-list 101 permit ip any 200.100.50.0 0.0.0.255 Implicit deny ip any any
    • 414. 414 Deny Destination Network access-list 101 deny ip 0.0.0.0 255.255.255.255 200.100.50.0 0.0.0.255 access-list 101 permit ip 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255 or access-list 101 deny ip any 200.100.50.0 0.0.0.255 access-list 101 permit ip any any Implicit deny ip any any is present but irrelevant.
    • 415. 415 Permit one Source Network to another Destination Network Assume the only traffic you want is traffic from network 200.100.50.0 to network 150.75.0.0 access-list 101 permit ip 200.100.50.0 0.0.0.255 150.75.0.0 0.0.255.255 Implicit deny ip any any To allow 2 way traffic between the networks add this statement: access-list 101 permit ip 150.75.0.0 0.0.255.255
    • 416. 416 Deny one Source Network to another Destination Network Assume you want to allow all traffic EXCEPT from network 200.100.50.0 to network 150.75.0.0 access-list 101 deny ip 200.100.50.0 0.0.0.255 150.75.0.0 0.0.255.255 access-list 101 permit ip any any To deny 2 way traffic between the networks add this statement: access-list 101 deny ip 150.75.0.0 0.0.255.255
    • 417. 417 Deny FTP Assume you do not want anyone FTPing on the network. access-list 101 deny tcp any any eq 21 access-list 101 permit ip any any or access-list 101 deny tcp any any eq ftp access-list 101 permit ip any any
    • 418. 418 Deny Telnet Assume you do not want anyone telnetting on the network. access-list 101 deny tcp any any eq 23 access-list 101 permit ip any any or access-list 101 deny tcp any any eq telnet access-list 101 permit ip any any
    • 419. 419 Deny Web Surfing Assume you do not want anyone surfing the internet. access-list 101 deny tcp any any eq 80 access-list 101 permit ip any any or access-list 101 deny tcp any any eq www access-list 101 permit ip any any You can also use http instead of www.
    • 420. 420 Complicated Example #1 Suppose you have the following conditions: • No one from Network 200.100.50.0 is allowed to FTP anywhere • Only hosts from network 150.75.0.0 may telnet to network 50.0.0.0 • Subnetwork 100.100.100.0/24 is not allowed to surf the internet access-list 101 deny tcp 200.100.50.0 0.0.0.255 any eq 21 access-list 101 permit tcp 150.75.0.0 0.0.255.255 50.0.0.0 0.255.255.255 eq 23 access-list 101 deny tcp any any eq 23 access-list 101 deny tcp 100.100.100.0 0.0.0.255 any eq 80
    • 421. 421 Complicated Example #2 Suppose you are the admin of network 200.100.50.0. You want to permit Email only between your network and network 150.75.0.0. You wish to place no restriction on other protocols like web surfing, ftp, telnet, etc. • Email server send/receive Protocol: SMTP, port 25 • User Check Email Protocol: POP3, port 110 This example assumes the your Email server is at addresses 200.100.50.25 access-list 101 permit tcp 200.100.50.0 0.0.0.255 150.75.0.0 0.0.255.255 eq 25 access-list 101 permit tcp 150.75.0.0 0.0.255.255 200.100.50.0 0.0.0.255 eq 25 access-list 101 permit tcp 200.100.50.0 0.0.0.255 200.100.50.0 0.0.0.255 eq 110 access-list 101 deny tcp any any smtp access-list 101 deny tcp any any pop3
    • 422. 422 NAT Network Address Translator Fig. 3 NAT (TI1332EU02TI_0003 New Address Concepts, 7)
    • 423. 423 New addressing concepts Problems with IPv4 Shortage of IPv4 addresses Allocation of the last IPv4 addresses is forecasted for the year 2005 Address classes were replaced by usage of CIDR, but this is not sufficient Short term solution NAT: Network Address Translator Long term solution IPv6 = IPng (IP next generation) Provides an extended address range Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 424. 424 NAT: Network Address Translator NAT Translates between local addresses and public ones Many private hosts share few global addresses Public Network Uses public addresses Public addresses are globally unique Private Network Uses private address range (local addresses) Local addresses may not be used externally Fig. 4 How does NAT work? (TI1332EU02TI_0003 New Address Concepts, 9)
    • 425. 425 NAT To be translated exclude reserve pool exclude realm with private addresses NAT Router realm with public addresses map translate Fig. 5 Translation mechanism (TI1332EU02TI_0003 New Address Concepts, 9)
    • 426. 426 free NAT Pool A timeout value (default 15 min) instructs NAT how long to keep an association in an idle state before returning the external IP address to the free NAT pool. Fig. 8 How does NAT know when to return the public IP address to the pool? (TI1332EU02TI_0003 New Address Concepts, 15)
    • 427. 427 NAT Addressing Terms • Inside Local – The term “inside” refers to an address used for a host inside an enterprise. It is the actual IP address assigned to a host in the private enterprise network. • Inside Global – NAT uses an inside global address to represent the inside host as the packet is sent through the outside network, typically the Internet. – A NAT router changes the source IP address of a packet sent by an inside host from an inside local address to an inside global address as the packet goes from the inside to the outside network.
    • 428. 428 NAT Addressing Terms • Outside Global – The term “outside” refers to an address used for a host outside an enterprise, the Internet. – An outside global is the actual IP address assigned to a host that resides in the outside network, typically the Internet. • Outside Local – NAT uses an outside local address to represent the outside host as the packet is sent through the private enterprise network. – A NAT router changes a packet’s destination IP address, sent from an outside global address to an inside host, as the packet goes from the outside to the inside network.
    • 429. 429 10.47.10.10 192.50.20.5 WAN Net A Net B LAN LAN 192.50.20.0 10.0.0.0 Router Router RouterRouter Router SA = 10.47.10.10SA = 10.47.10.10 DA = 192.50.20.5DA = 192.50.20.5 SA = 193.50.30.4SA = 193.50.30.4 DA = 192.50.20.5DA = 192.50.20.5 Router A with NATRouter A with NAT Router BRouter B Fig. 7 An example for NAT (TI1332EU02TI_0003 New Address Concepts, 13)
    • 430. 430 WAN 138.76.29.7 Net A 10.0.0.0/8 Router Router Router SA = 10.0.0.10SA = 10.0.0.10 DA = 138.76.29.7DA = 138.76.29.7 SA = 138.76.28.4SA = 138.76.28.4 DA =138.76.29.7DA =138.76.29.7 NAT with WAN interface: 138.76.28.4 NAT with WAN interface: 138.76.28.4 SA = 138.76.29.7SA = 138.76.29.7 DA = 138.76.28.4DA = 138.76.28.4 SA = 138.76.29.7SA = 138.76.29.7 DA = 10.0.0.10DA = 10.0.0.10 10.0.0.10 Fig. 11 An example for NAPT (TI1332EU02TI_0003 New Address Concepts, 21)
    • 431. 431 Types Of NAT • There are different types of NAT that can be used, which are – Static NAT – Dynamic NAT – Overloading NAT with PAT (NAPT)
    • 432. 432 Static NAT • With static NAT, the NAT router simply configures a one-to-one mapping between the private address and the registered address that is used on its behalf.
    • 433. 433
    • 434. 434 Dynamic NAT • Like static NAT, the NAT router creates a one-to-one mapping between an inside local and inside global address and changes the IP addresses in packets as they exit and enter the inside network. • However, the mapping of an inside local address to an inside global address happens dynamically.
    • 435. 435 Dynamic NAT • Dynamic NAT sets up a pool of possible inside global addresses and defines criteria for the set of inside local IP addresses whose traffic should be translated with NAT. • The dynamic entry in the NAT table stays in there as long as traffic flows occasionally.
    • 436. 436 PAT Port Address Translator Fig. 9 NAPT (TI1332EU02TI_0003 New Address Concepts, 17)
    • 437. 437 WAN 138.76.29.7 Net A 10.0.0.0/8 Router Router Router SA = 10.0.0.10, sport = 3017SA = 10.0.0.10, sport = 3017 DA = 138.76.29.7, dpor t= 23DA = 138.76.29.7, dpor t= 23 SA = 138.76.28.4, sport = 1024SA = 138.76.28.4, sport = 1024 DA =138.76.29.7, dpor t= 23DA =138.76.29.7, dpor t= 23 NAPT with WAN interface: 138.76.28.4 NAPT with WAN interface: 138.76.28.4 SA = 138.76.29.7, spor t= 23SA = 138.76.29.7, spor t= 23 DA = 138.76.28.4, dport = 1024DA = 138.76.28.4, dport = 1024 SA = 138.76.29.7, spor t= 23SA = 138.76.29.7, spor t= 23 DA = 10.0.0.10, dport = 3017DA = 10.0.0.10, dport = 3017 10.0.0.10 Fig. 11 An example for NAPT (TI1332EU02TI_0003 New Address Concepts, 21)
    • 438. 438 WAN private IP network (e.g. SOHO) registered IP @, assigned TU port # local IP @, local TU port # single public IP address mapping pool of TU port numbers PAT with e.g. a single public IP addressPAT with e.g. a single public IP address TU....TCP/UDP Fig. 10 NAPT (TI1332EU02TI_0003 New Address Concepts, 19)
    • 439. 439 NAT&PAT Network Address Translation & Port Address Transation Fig. 3 NAT (TI1332EU02TI_0003 New Address Concepts, 7)
    • 440. 440 New addressing concepts Problems with IPv4 Shortage of IPv4 addresses Allocation of the last IPv4 addresses is forecasted for the year 2006 Address classes were replaced by usage of CIDR, but this is not sufficient Short term solution NAT: Network Address Translator Long term solution IPv6 = IPng (IP next generation) Provides an extended address range Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 441. 441 NAT: Network Address Translator NAT Translates between local addresses and public ones Many private hosts share few global addresses Public Network Uses public addresses Public addresses are globally unique Private Network Uses private address range (local addresses) Local addresses may not be used externally Fig. 4 How does NAT work? (TI1332EU02TI_0003 New Address Concepts, 9)
    • 442. 442 NAT To be translated exclude reserve pool exclude private addresses NAT Router public addresses map translate Fig. 5 Translation mechanism (TI1332EU02TI_0003 New Address Concepts, 9)
    • 443. 443 free NAT Pool A timeout value (default 15 min) instructs NAT how long to keep an association in an idle state before returning the external IP address to the free NAT pool. Fig. 8 How does NAT know when to return the public IP address to the pool? (TI1332EU02TI_0003 New Address Concepts, 15)
    • 444. 444 NAT Addressing Terms • Inside Local “Private address” – The term “inside” refers to an address used for a host inside an enterprise. It is the actual IP address assigned to a host in the private enterprise network. • Inside Global “Public address” – NAT uses an inside global address to represent the inside host as the packet is sent through the outside network, typically the WAN. – A NAT router changes the source IP address of a packet sent by an inside host from an inside local address to an inside global address as the packet goes from the inside to the outside network.Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 445. 445 10.47.10.10 192.50.20.5 WAN Net A Net B LAN LAN 192.50.20.0 10.0.0.0 Router Router RouterRouter Router SA = 10.47.10.10SA = 10.47.10.10 DA = 192.50.20.5DA = 192.50.20.5 SA = 193.50.30.4SA = 193.50.30.4 DA = 192.50.20.5DA = 192.50.20.5 Router A with NATRouter A with NAT Router BRouter B Fig. 7 An example for NAT (TI1332EU02TI_0003 New Address Concepts, 13)
    • 446. 446 WAN 138.76.29.7 Net A 10.0.0.0/8 Router Router Router SA = 10.0.0.10SA = 10.0.0.10 DA = 138.76.29.7DA = 138.76.29.7 SA = 138.76.28.4SA = 138.76.28.4 DA =138.76.29.7DA =138.76.29.7 NAT with WAN interface: 138.76.28.4 NAT with WAN interface: 138.76.28.4 SA = 138.76.29.7SA = 138.76.29.7 DA = 138.76.28.4DA = 138.76.28.4 SA = 138.76.29.7SA = 138.76.29.7 DA = 10.0.0.10DA = 10.0.0.10 10.0.0.10 Fig. 11 An example for NAPT (TI1332EU02TI_0003 New Address Concepts, 21)
    • 447. 447 Types Of NAT • There are different types of NAT that can be used, which are – Static NAT – Dynamic NAT – Overloading NAT with PAT (NAT Over PAT) Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 448. 448 Static NAT • With static NAT, the NAT router simply configures a one-to-one mapping between the private address and the registered address that is used on its behalf. Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 449. 449
    • 450. 450 Static NAT Configuration • To form NAT table Router(config)#IP Nat inside source static [inside local source IP address] [inside global source IP address] Router(config)#IP Nat inside source static [inside local source IP address] [inside global source IP address] • Assign NAT to an Interface Router(config)#Interface [Serial x/y] Router(config-if)#IP NAT [Inside] Router(config)#Interface [Serial x/y] Router(config-if)#IP NAT [Inside] • See Example Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 451. 451 Dynamic NAT • Like static NAT, the NAT router creates a one-to-one mapping between an inside local and inside global address and changes the IP addresses in packets as they exit and enter the inside network. • However, the mapping of an inside local address to an inside global address happens dynamically. Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 452. 452 Dynamic NAT • Dynamic NAT sets up a pool of possible inside global addresses and defines criteria for the set of inside local IP addresses whose traffic should be translated with NAT. • The dynamic entry in the NAT table stays in there as long as traffic flows occasionally. • If a new packet arrives, and it needs a NAT entry, but all the pooled IP addresses are inFig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 453. 453 Dynamic NAT Configuration • Specify inside addresses to be translated Router(config)#IP Nat inside source list [standard Access List number] pool [NAT Pool Name] Router(config)#IP Nat inside source list [standard Access List number] pool [NAT Pool Name] • Specify NAT pool Router(config)#IP Nat pool [NAT Pool Name] [First inside global address] [Last inside global address] netmask [subnet mask] Router(config)#IP Nat pool [NAT Pool Name] [First inside global address] [Last inside global address] netmask [subnet mask] • Assign NAT to an Interface Router(config)#Interface [Serial x/y] Router(config-if)#IP NAT [Inside] Router(config)#Interface [Serial x/y] Router(config-if)#IP NAT [Inside] • See Example Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 454. 454 PAT Port Address Translator Fig. 9 NAPT (TI1332EU02TI_0003 New Address Concepts, 17)
    • 455. 455 WAN 138.76.29.7 Net A 10.0.0.0/8 Router Router Router SA = 10.0.0.10, sport = 3017SA = 10.0.0.10, sport = 3017 DA = 138.76.29.7, dpor t= 23DA = 138.76.29.7, dpor t= 23 SA = 138.76.28.4, sport = 1024SA = 138.76.28.4, sport = 1024 DA =138.76.29.7, dpor t= 23DA =138.76.29.7, dpor t= 23 NAPT with WAN interface: 138.76.28.4 NAPT with WAN interface: 138.76.28.4 SA = 138.76.29.7, spor t= 23SA = 138.76.29.7, spor t= 23 DA = 138.76.28.4, dport = 1024DA = 138.76.28.4, dport = 1024 SA = 138.76.29.7, spor t= 23SA = 138.76.29.7, spor t= 23 DA = 10.0.0.10, dport = 3017DA = 10.0.0.10, dport = 3017 10.0.0.10 Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 456. 456 WAN private IP network (e.g. SOHO) registered IP @, assigned TU port # local IP @, local TU port # single public IP address mapping pool of TU port numbers PAT with e.g. a single public IP addressPAT with e.g. a single public IP address TU....TCP/UDP Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 457. 457 PAT Configuration • Specify inside addresses to be translated Router(config)#IP Nat inside source list [standard Access List number] pool [NAT Pool Name] overload Router(config)#IP Nat inside source list [standard Access List number] pool [NAT Pool Name] overload • Specify PAT pool Router(config)#IP Nat pool [NAT Pool Name] [First inside global address] [Last inside global address] netmask [subnet mask] Router(config)#IP Nat pool [NAT Pool Name] [First inside global address] [Last inside global address] netmask [subnet mask] • Assign PAT to an Interface Router(config)#Interface [Serial x/y] Router(config-if)#IP NAT [Inside] Router(config)#Interface [Serial x/y] Router(config-if)#IP NAT [Inside] • See Example Fig. 2 Address shortage and possible solutions (TI1332EU02TI_0003 New Address Concepts, 5)
    • 458. 458
    • 459. 459 Ethernet Access with Hubs
    • 460. 460 Ethernet Access with Bridges
    • 461. 461 Ethernet Access with Switches
    • 462. 462 Today's LAN
    • 463. 463 Full Duplex Transmitting Full-duplex Ethernet allows the transmission of a packet and the reception of a different packet at the same time. This simultaneous transmission and reception requires the use of two pairs of wires in the cable and a switched connection between each node. This connection is considered point-to-point and is collision free. The full-duplex Ethernet switch takes advantage of the two pairs of wires in the cable by creating a direct connection between the transmit (TX) at one end of the circuit and the receive (RX) at the other end. Ethernet usually can only use 50%-60% of the available 10 Mbps of bandwidth because of collisions and latency. Full-duplex Ethernet offers 100% of the bandwidth in both directions. This produces a potential 20 Mbps throughput.
    • 464. 464
    • 465. 465 Collision Domains
    • 466. 466 Segmentation with Bridges
    • 467. 467 Segmentation with Routers
    • 468. 468 Segmentation with Switches
    • 469. 469 Basic Operations of a Switch Switching is a technology that decreases congestion in Ethernet, Token Ring, and FDDI LANs. Switching accomplishes this by reducing traffic and increasing bandwidth. LAN switches are often used to replace shared hubs and are designed to work with existing cable infrastructures. Switching equipment performs the following two basic operations: • Switching data frames • Maintaining switching operations  
    • 470. 470 Switching Methods 1. Store-and-Forward The entire frame is received before any forwarding takes place. Filters are applied before the frame is forwarded. Most reliable and also most latency especially when frames are large. 2. Cut-Through The frame is forwarded through the switch before the entire frame is received. At a minimum the frame destination address must be read before the frame can be forwarded. This mode decreases the latency of the transmission, but also reduces error detection.  3. Fragment-Free Fragment-free switching filters out collision fragments before forwarding begins. Collision fragments are the majority of packet errors. In a properly functioning network, collision fragments must be smaller than 64 bytes. Anything > 64 bytes is a valid packet and is usually received without error.
    • 471. 471 Frame Transmission Modes
    • 472. 472 Benefits of Switching
    • 473. 473 How Switches and Bridges Learn Addresses Bridges and switches learn in the following ways: • Reading the source MAC address of each received frame or datagram • Recording the port on which the MAC address was received. In this way, the bridge or switch learns which addresses belong to the devices connected to each port.
    • 474. 474 CAM Content Addressable Memory CAM is used in switch applications: • To take out and process the address information from incoming data packets • To compare the destination address with a table of addresses stored within it The CAM stores host MAC addresses and associated port numbers. The CAM compares the received destination MAC address against the CAM table contents. If the comparison yields a match, the port is provided, and switching control forwards the packet to the correct port
    • 475. 475 Shared vs. Dedicates Bandwidth If a hub is used, bandwidth is shared. If a switch is used, then bandwidth is dedicated. If a workstation or server is directly connected to a switch port, then the full bandwidth of the connection to the switch is available to the connected computer. If a hub is connected to a switch port, bandwidth is shared between all devices connected to the hub.
    • 476. 476 Microsegmentation of a Network
    • 477. 477 Microsegmentation
    • 478. 478 3 Methods of Communication
    • 479. 479 Switches & Broadcast Domains When two switches are connected, the broadcast domain is increased. The overall result is a reduction in available bandwidth. This happens because all devices in the broadcast domain must receive and process the broadcast frame. Routers are Layer 3 devices. Routers do not propagate broadcasts. Routers are used to segment both collision and broadcast domains.
    • 480. 480 Broadcast Domain
    • 481. 481
    • 482. 482 Overview To design reliable, manageable, and scalable networks, a network designer must realize that each of the major components of a network has distinct design requirements. Good network design will improve performance and also reduce the difficulties associated with network growth and evolution. The design of larger LANs includes identifying the following: • An access layer that connects end users into the LAN • A distribution layer that provides policy-based connectivity between end-user LANs • A core layer that provides the fastest connection between the distribution points Each of these LAN design layers requires switches that are best suited for specific tasks.
    • 483. 483 The Access Layer The access layer is the entry point for user workstations and servers to the network. In a campus LAN the device used at the access layer can be a switch or a hub. Access layer functions also include MAC layer filtering and microsegmentation. Layer 2 switches are used in the access layer.
    • 484. 484 Access Layer Switches Access layer switches operate at Layer 2 of the OSI model The main purpose of an access layer switch is to allow end users into the network. An access layer switch should provide this functionality with low cost and high port density. The following Cisco switches are commonly used at the access layer: • Catalyst 1900 series • Catalyst 2820 series • Catalyst 2950 series • Catalyst 4000 series • Catalyst 5000 series
    • 485. 485 The Distribution Layer The distribution layer of the network is between the access and core layers. Networks are segmented into broadcast domains by this layer. Policies can be applied and access control lists can filter packets. The distribution layer isolates network problems to the workgroups in which they occur. The distribution layer also prevents these problems from affecting the core layer. Switches in this layer operate at Layer 2 and Layer 3.
    • 486. 486 Distribution Layer Switches The distribution layer switch must have high performance. The distribution layer switch is a point at which a broadcast domain is delineated. It combines VLAN traffic and is a focal point for policy decisions about traffic flow. For these reasons distribution layer switches operate at both Layer 2 and Layer 3 of the OSI model. Switches in this layer are referred to as multilayer switches. These multilayer switches combine the functions of a router and a switch in one device. The following Cisco switches are suitable for the distribution layer:  • Catalyst 2926G • Catalyst 5000 family • Catalyst 6000 family
    • 487. 487 The Core Layer The core layer is a high-speed switching backbone. This layer of the network design should not perform any packet manipulation. Packet manipulation, such as access list filtering, would slow down the process. Providing a core infrastructure with redundant alternate paths gives stability to the network in the event of a single device failure. The core can be designed to use Layer 2 or Layer 3 switching. Asynchronous Transfer Mode (ATM) or Ethernet switches can be used.
    • 488. 488 Core Layer Switches The switches in this layer can make use of a number of Layer 2 technologies. Provided that the distance between the core layer switches is not too great, the switches can use Ethernet technology. In a network design, the core layer can be a routed, or Layer 3, core. Core layer switches are designed to provide efficient Layer 3 functionality when needed. Factors such as need, cost, and performance should be considered before a choice is made. The following Cisco switches are suitable for the core layer: • Catalyst 6500 series • Catalyst 8500 series • IGX 8400 series • Lightstream 1010
    • 489. 489
    • 490. 490 Physical Startup of the Catalyst SwitchSwitches are dedicated, specialized computers, which contain a CPU, RAM, and an operating system. Switches usually have several ports for the purpose of connecting hosts, as well as specialized ports for the purpose of management. A switch can be managed by connecting to the console port to view and make changes to the configuration. Switches typically have no power switch to turn them on and off. They simply connect or disconnect from a power source. Several switches from the Cisco Catalyst 2950 series are shown in graphic to the
    • 491. 491 Switch LED Indicators The front panel of a switch has several lights to help monitor system activity and performance. These lights are called light-emitting diodes (LEDs). The switch has the following LEDs: • System LED • Remote Power Supply (RPS) LED • Port Mode LED • Port Status LEDs The System LED shows whether the system is receiving power and functioning correctly. The RPS LED indicates whether or not the remote power supply is in use. The Mode LEDs indicate the current state of the Mode button. The Port Status LEDs have different meanings, depending on the current value of the Mode LED.
    • 492. 492 Verifying Port LEDs During Switch POST Once the power cable is connected, the switch initiates a series of tests called the power-on self test (POST). POST runs automatically to verify that the switch functions correctly. The System LED indicates the success or failure of POST.
    • 493. 493 Connecting a Switch to a Computer
    • 494. 494 Examining Help in the Switch CLI The command-line interface (CLI) for Cisco switches is very similar to the CLI for Cisco routers. The help command is issued by entering a question mark (?). When this command is entered at the system prompt, a list of commands available for the current command mode is displayed. The help command is very flexible and essentially functions the same way it does in a router CLI. This form of help is called command syntax help, because it provides applicable keywords or arguments
    • 495. 495 Switch Command Modes Switches have several command modes. The default mode is User EXEC mode, which ends in a greater-than character (>). The commands available in User EXEC mode are limited to those that change terminal settings, perform basic tests, and display system information. The enable command is used to change from User EXEC mode to Privileged EXEC mode, which ends in a pound- sign character (#). The configure command allows other command modes to be accessed.   
    • 496. 496 Show Commands in User-Exec Mode
    • 497. 497 Setting Switch Hostname Setting Passwords on Lines
    • 498. 498
    • 499. 499 Overview Redundancy in a network is extremely important because redundancy allows networks to be fault tolerant. Redundant topologies based on switches and bridges are susceptible to broadcast storms, multiple frame transmissions, and MAC address database instability. Therefore network redundancy requires careful planning and monitoring to function properly. The Spanning-Tree Protocol is used in switched networks to create a loop free logical topology from
    • 500. 500 Redundant Switched Topologies Networks with redundant paths and devices allow for more network uptime. In the graphic, if Switch A fails, traffic can still flow from Segment 2 to Segment 1 and to the router through Switch B. If port 1 fails on Switch A then traffic can still flow through port 1 on Switch B. Switches learn the MAC addresses of devices on their ports so that data can be properly forwarded to the destination. Switches will flood frames for unknown destinations until they learn the MAC addresses of the devices. A redundant switched topology may cause broadcast storms, multiple frame copies, and MAC address table instability problems.
    • 501. 501 Broadcast Storms Broadcasts and multicasts can cause problems in a switched network. Multicasts are treated as broadcasts by the switches. Broadcasts and multicasts frames are flooded out all ports, except the one on which the frame was received. The switches continue to propagate broadcast traffic over and over. This is called a broadcast storm. This will continue until one of the switches is disconnected. The network will appear to be down or extremely slow.
    • 502. 502 Multiple Frame Transmissions In a redundant switched network it is possible for an end device to receive multiple frames. Assume that the MAC address of Router Y has been timed out by both switches. Also assume that Host X still has the MAC address of Router Y in its ARP cache and sends a unicast frame to Router Y. The router receives the frame because it is on the same segment as Host X. Switch A does not have the MAC address of the Router Y and will therefore flood the frame out its ports. Switch B also does not know which port Router Y is on. Switch B then floods the frame it received causing Router Y to receive multiple copies of the same frame. This is a cause of unnecessary processing in all devices.
    • 503. 503 MAC Database Instability A switch can incorrectly learn that a MAC address is on one port, when it is actually on a different port. In this example the MAC address of Router Y is not in the MAC address table of either switch. Host X sends a frame directed to Router Y. Switches A & B learn the MAC address of Host X on port 0. The frame to Router Y is flooded on port 1 of both switches. Switches A and B see this information on port 1 and incorrectly learn the MAC address of Host X on port 1. When Router Y sends a frame to Host X, Switch A and Switch B will also receive the frame and will send it out port 1. This is unnecessary, but the switches have incorrectly learned that Host X is on port 1.
    • 504. 504 Using Bridging Loops for Redundancy
    • 505. 505 Logical Loop Free Topology Created with STP
    • 506. 506 NOTE: Don’t confuse Spanning Tree Protocol (STP) with Shielded Twisted Pair (STP).
    • 507. 507 Spanning Tree Protocol - 1 Ethernet bridges and switches can implement the IEEE 802.1D Spanning-Tree Protocol and use the spanning-tree algorithm to construct a loop free shortest path network. Shortest path is based on cumulative link costs. Link costs are based on the speed of the link.
    • 508. 508 Spanning Tree Protocol - 2 The Spanning-Tree Protocol establishes a root node, called the root bridge/switch. The Spanning-Tree Protocol constructs a topology that has one path for reaching every network node. The resulting tree originates from the root bridge/switch. The Spanning-Tree Protocol requires network devices to exchange messages to detect bridging loops. Links that will cause a loop are put into a blocking state. The message that a switch sends, allowing the formation of a loop free logical topology, is called a Bridge Protocol Data Unit (BPDU).
    • 509. 509 Selecting the Root Bridge The first decision that all switches in the network make, is to identify the root bridge. The position of the root bridge in a network will affect the traffic flow. When a switch is turned on, the spanning-tree algorithm is used to identify the root bridge. BPDUs are sent out with the Bridge ID (BID). The BID consists of a bridge priority that defaults to 32768 and the switch base MAC address. When a switch first starts up, it assumes it is the root switch and sends BPDUs. These BPDUs contain the switch MAC address in both the root and sender BID. As a switch receives a BPDU with a lower root BID it replaces that in the BPDUs that are sent out. All bridges see these and decide that the bridge with the smallest BID value will be the root bridge. A network administrator may want to influence the decision by setting the switch priority to a smaller value than the default.
    • 510. 510 BDPUs BPDUs contain enough information so that all switches can do the following: • Select a single switch that will act as the root of the spanning tree • Calculate the shortest path from itself to the root switch • Designate one of the switches as the closest one to the root, for each LAN segment. This bridge is called the “designated switch”. The designated switch handles all communication from that LAN towards the root bridge. • Each non-root switch choose one of its ports as its root port, this is the interface that gives the best path to the root switch. • Select ports that are part of the spanning tree, the designated ports. Non-designated ports are blocked.
    • 511. 511 Spanning Tree Operation When the network has stabilized, it has converged and there is one spanning tree per network. As a result, for every switched network the following elements exist: • One root bridge per network • One root port per non root bridge • One designated port per segment • Unused, non-designated ports Root ports and designated ports are used for forwarding (F) data traffic. Non-designated ports discard data traffic. Non-designated ports are called blocking (B) or discarding ports.
    • 512. 512 Spanning Tree Port States
    • 513. 513 Spanning Tree Recalculation A switched internetwork has converged when all the switch and bridge ports are in either the forwarding or blocked state. Forwarding ports send and receive data traffic and BPDUs. Blocked ports will only receive BPDUs. When the network topology changes, switches and bridges recompute the Spanning Tree and cause a disruption of user traffic. Convergence on a new spanning-tree topology using the IEEE 802.1D standard can take up to 50 seconds. This convergence is made up of the max-age of 20 seconds, plus the listening forward delay of 15 seconds, and the learning forward delay of 15 seconds.
    • 514. 514 Rapid STP Designations
    • 515. 515
    • 516. 516 VLANs VLAN implementation combines Layer 2 switching and Layer 3 routing technologies to limit both collision domains and broadcast domains. VLANs can also be used to provide security by creating the VLAN groups according to function and by using routers to communicate between VLANs. A physical port association is used to implement VLAN assignment. Communication between VLANs can occur only through the router. This limits the size of the broadcast domains and uses the router to determine whether one VLAN can talk to another VLAN. NOTE: This is the only way a switch can break up a broadcast domain!
    • 517. 517 Setting up VLAN Implementation
    • 518. 518 VLAN Communication
    • 519. 519 VLAN Membership Modes • VLAN membership can either be static or dynamic.
    • 520. 520 • All users attached to same switch port must be in the same VLAN. Static VLANs
    • 521. 521 Configuring VLANs in Global Mode Switch#configure terminal Switch(config)#vlan 3 Switch(config-vlan)#name Vlan3 Switch(config-vlan)#exit Switch(config)#end
    • 522. 522 Configuring VLANs in VLAN Database Mode Switch#vlan database Switch(vlan)#vlan 3 VLAN 3 added: Name: VLAN0003 Switch(vlan)#exit APPLY completed. Exiting....
    • 523. 523 Deleting VLANs in Global Mode Switch#configure terminal Switch(config)#no vlan 3 Switch(config)#end
    • 524. 524 Deleting VLANs in VLAN Database Mode Switch#vlan database Switch(vlan)#no vlan 3 VLAN 3 deleted: Name: VLAN0003 Switch(vlan)#exit APPLY completed. Exiting....
    • 525. 525 Assigning Access Ports to a VLAN Switch(config)#interface gigabitethernet 1/1Switch(config)#interface gigabitethernet 1/1 • Enters interface configuration mode Switch(config-if)#switchport mode accessSwitch(config-if)#switchport mode access • Configures the interface as an access port Switch(config-if)#switchport access vlan 3Switch(config-if)#switchport access vlan 3 • Assigns the access port to a VLAN
    • 526. 526 Verifying the VLAN Configuration Switch#show vlan [id | name] [vlan_num | vlan_name]Switch#show vlan [id | name] [vlan_num | vlan_name] VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/1, Fa0/2, Fa0/5, Fa0/7 Fa0/8, Fa0/9, Fa0/11, Fa0/12 Gi0/1, Gi0/2 2 VLAN0002 active 51 VLAN0051 active 52 VLAN0052 active … VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2 ---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------ 1 enet 100001 1500 - - - - - 1002 1003 2 enet 100002 1500 - - - - - 0 0 51 enet 100051 1500 - - - - - 0 0 52 enet 100052 1500 - - - - - 0 0 … Remote SPAN VLANs ------------------------------------------------------------------------------ Primary Secondary Type Ports ------- --------- ----------------- ------------------------------------------
    • 527. 527 Verifying the VLAN Port Configuration Switch#show running-config interface {fastethernet | gigabitethernet} slot/port Switch#show running-config interface {fastethernet | gigabitethernet} slot/port • Displays the running configuration of the interface Switch#show interfaces [{fastethernet | gigabitethernet} slot/port] switchport Switch#show interfaces [{fastethernet | gigabitethernet} slot/port] switchport • Displays the switch port configuration of the interface Switch#show mac-address-table interface interface-id [vlan vlan-id] [ | {begin | exclude | include} expression] Switch#show mac-address-table interface interface-id [vlan vlan-id] [ | {begin | exclude | include} expression] • Displays the MAC address table information for the specified interface in the specified VLAN
    • 528. 528 Implementing VLAN Trunks © 2003, Cisco Systems, Inc. All rights reserved. BCMSN v2.0—2-528
    • 529. 529 VLAN Trunking
    • 530. 530 Importance of Native VLANs
    • 531. 531 – Performed with ASIC – Not intrusive to client stations; client does not see the header – Effective between switches, and between routers and switches ISL Encapsulation
    • 532. 532 ISL and Layer 2 Encapsulation
    • 533. 533 Configuring ISL Trunking Switch(config)#interface fastethernet 2/1Switch(config)#interface fastethernet 2/1 Switch(config-if)#switchport mode trunkSwitch(config-if)#switchport mode trunk Switch(config-if)#switchport trunk encapsulation [isl|dot1q]Switch(config-if)#switchport trunk encapsulation [isl|dot1q] •Enters interface configuration mode •Selects the encapsulation • Configures the interface as a Layer 2 trunk
    • 534. 534 Verifying ISL Trunking Switch#show running-config interface {fastethernet | gigabitethernet} slot/port Switch#show running-config interface {fastethernet | gigabitethernet} slot/port Switch#show interfaces [fastethernet | gigabitethernet] slot/port [ switchport | trunk ] Switch#show interfaces [fastethernet | gigabitethernet] slot/port [ switchport | trunk ] Switch#show interfaces fastethernet 2/1 trunk Port Mode Encapsulation Status Native VLAN Fa2/1 desirable isl trunking 1 Port VLANs allowed on trunk Fa2/1 1-1005 Port VLANs allowed and active in management domain Fa2/1 1-2,1002-1005 Port VLANs in spanning tree forwarding state and not pruned Fa2/1 1-2,1002-1005
    • 535. 535 802.1Q Trunking
    • 536. 536 Configuring 802.1Q Trunking Switch(config)#interface fastethernet 5/8 Switch(config-if)#shutdown Switch(config-if)#switchport trunk encapsulation dot1q Switch(config-if)#switchport trunk allowed vlan 1,15,11,1002-1005 Switch(config-if)#switchport mode trunk Switch(config-if)#switchport nonegotiate Switch(config-if)#no shutdown
    • 537. 537 Verifying 802.1Q Trunking Switch#show running-config interface {fastethernet | gigabitethernet} slot/port Switch#show running-config interface {fastethernet | gigabitethernet} slot/port Switch#show interfaces [fastethernet | gigabitethernet] slot/port [ switchport | trunk ] Switch#show interfaces [fastethernet | gigabitethernet] slot/port [ switchport | trunk ] Switch#show interfaces gigabitEthernet 0/1 switchport Name: Gi0/1 Switchport: Enabled Administrative Mode: trunk Operational Mode: trunk Administrative Trunking Encapsulation: dot1q Operational Trunking Encapsulation: dot1q Negotiation of Trunking: On Access Mode VLAN: 1 (default) Trunking Native Mode VLAN: 1 (default) Trunking VLANs Enabled: ALL Pruning VLANs Enabled: 2-1001 . . .
    • 538. 538 Implementing VLAN Trunk Protocol © 2003, Cisco Systems, Inc. All rights reserved. BCMSN 2.0—2-538
    • 539. 539 – Advertises VLAN configuration information – Maintains VLAN configuration consistency throughout a common administrative domain – Sends advertisements on trunk ports only VTP Protocol Features
    • 540. 540 • Cannot create, change, or delete VLANs • Forwards advertisements • Synchronizes VLAN configurations • Does not save in NVRAM •Creates, modifies, and deletes VLANs •Sends and forwards advertisements •Synchronizes VLAN configurations •Saves configuration in NVRAM •Creates, modifies, and deletes VLANs locally only •Forwards advertisements •Does not synchronize VLAN configurations •Saves configuration in NVRAM VTP Modes
    • 541. 541 VTP Operation • VTP advertisements are sent as multicast frames. • VTP servers and clients are synchronized to the latest update identified revision number. • VTP advertisements are sent every 5 minutes or when there is a change.
    • 542. 542 • Increases available bandwidth by reducing unnecessary flooded traffic • Example: Station A sends broadcast, and broadcast is flooded only toward any switch with ports assigned to the red VLAN. VTP Pruning
    • 543. 543 VTP Configuration Guidelines – Configure the following: • VTP domain name • VTP mode (server mode is the default) • VTP pruning • VTP password – Be cautious when adding a new switch into an existing domain. – Add a new switch in a Client mode to get the last up-to-date information from the network then convert it to Server mode. – Add all new configurations to switch in transparent mode and check your configuration well then convert it to Server mode to prevent the switch from propagating incorrect VLAN information.
    • 544. 544 Configuring a VTP Server Switch(config)#vtp serverSwitch(config)#vtp server • Configures VTP server mode Switch(config)#vtp domain domain-nameSwitch(config)#vtp domain domain-name • Specifies a domain name Switch(config)#vtp password passwordSwitch(config)#vtp password password • Sets a VTP password Switch(config)#vtp pruningSwitch(config)#vtp pruning • Enables VTP pruning in the domain
    • 545. 545 Configuring a VTP Server (Cont.) Switch#configure terminal Switch(config)#vtp server Setting device to VTP SERVER mode. Switch(config)#vtp domain Lab_Network Setting VTP domain name to Lab_Network Switch(config)#end
    • 546. 546 Verifying the VTP Configuration Switch#show vtp statusSwitch#show vtp status Switch#show vtp status VTP Version : 2 Configuration Revision : 247 Maximum VLANs supported locally : 1005 Number of existing VLANs : 33 VTP Operating Mode : Client VTP Domain Name : Lab_Network VTP Pruning Mode : Enabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled MD5 digest : 0x45 0x52 0xB6 0xFD 0x63 0xC8 0x49 0x80 Configuration last modified by 0.0.0.0 at 8-12-99 15:04:49 Switch#
    • 547. 547 Verifying the VTP Configuration (Cont.) Switch#show vtp countersSwitch#show vtp counters Switch#show vtp counters VTP statistics: Summary advertisements received : 7 Subset advertisements received : 5 Request advertisements received : 0 Summary advertisements transmitted : 997 Subset advertisements transmitted : 13 Request advertisements transmitted : 3 Number of config revision errors : 0 Number of config digest errors : 0 Number of V1 summary errors : 0 VTP pruning statistics: Trunk Join Transmitted Join Received Summary advts received from non-pruning-capable device ---------------- ---------------- ---------------- --------------------------- Fa5/8 43071 42766 5
    • 548. 548
    • 549. 549 Contents • Remote access overview • WAN Connection Types • Defining WAN Encapsulation Protocols • Determining the WAN Type to Use • OSI Layer-2 Point-to-Point WANs – PPP – HDLC – Frame Relay
    • 550. 550 Remote Access Overview • A WAN is a data communications network covering a relatively broad geographical area. • A network administrator designing a remote network must weight issues concerning users needs such as bandwidth and cost of the variable available technologies.
    • 551. 551 WAN Connection Types
    • 552. 552 WAN Connection Types • Leased lines – It is a pre-established WAN communications path from the CPE, through the DCE switch, to the CPE of the remote site, allowing DTE networks to communicate at any time with no setup procedures before transmitting data. • Circuit switching – Sets up line like a phone call. No data can transfer before the end-to-end connection is established.
    • 553. 553 WAN Connection Types • Packet switching – WAN switching method that allows you to share bandwidth with other companies to save money. As long as you are not constantly transmitting data and are instead using bursty data transfers, packet switching can save you a lot of money. – However, if you have constant data transfers, then you will need to get a leased line. – Frame Relay and X.25 are packet switching technologies.
    • 554. 554 Defining WAN Encapsulation Protocols • Each WAN connection uses an encapsulation protocol to encapsulate traffic while it crossing the WAN link. • The choice of the encapsulation protocol depends on the underlying WAN technology and the communicating equipment.
    • 555. 555 Defining WAN Encapsulation Protocols • Typical WAN encapsulation types include the following: – Point-to-Point Protocol (PPP) – Serial Line Internet Protocol (SLIP) – High-Level Data Link Control Protocol (HDLC) – X.25 / Link Access Procedure Balanced (LAPB) – Frame Relay – Asynchronous Transfer Mode (ATM)
    • 556. 556 Determining the WAN Type to Use • Availability – Each type of service may be available in certain geographical areas. • Bandwidth – Determining usage over the WAN is important to evaluate the most cost-effective WAN service. • Cost – Making a compromise between the traffic you need to transfer and the type of service with the available cost that will suit you.
    • 557. 557 Determining the WAN Type to Use • Ease of Management – Connection management includes both the initial start-up configuration and the outgoing configuration of the normal operation. • Application Traffic – Traffic may be as small as during a terminal session , or very large packets as during file transfer.
    • 558. 558 Max. WAN Speeds for WAN Connections WAN Type Maximum Speed Asynchronous Dial-Up 56-64 Kbps X.25, ISDN – BRI 128 Kbps ISDN – PRI E1 / T1 Leased Line / Frame Relay E3 / T3
    • 559. 559 OSI Layer-2 Point-to-Point WANs • WAN protocols used on Point-to-Point serial links provide the basic function of data delivery across that one link. • The two most popular data link protocols used today are Point-to- Point Protocol (PPP) and High-Level Data Link Control (HDLC).
    • 560. 560 HDLC • HDLC performs OSI Layer-2 functions. • It determines when it is appropriate to use the physical medium. • Ensures that the correct recipient receives and processes the data that is sent. • Determines whether the sent data was received correctly or not (error detection).
    • 561. 561 HDLC • HDLC Frame Format • The original HDLC didn’t include any Protocol Type field, every company (including Cisco) added its own field, so it became a proprietary protocol that can be used between only Cisco routers.
    • 562. 562 Point-to-Point Protocol (PPP) • PPP is a standard encapsulation protocol for the transport of different Network Layer protocols (including, but not limited to, IP). • It has the following main functional components – Link Control Protocol (LCP) that establishes, authenticates, and tests the data link connection. – Network Control Protocols (NCPs) that establishes and configure different network layer protocols.
    • 563. 563 Point-to-Point Protocol (PPP) • PPP discards frames that do not pass the error check. • PPP is a standard protocol, and so it can be used with all types of routers (not Cisco Proprietary).
    • 564. 564 PPP LCP Features • Authentication • Compression • Multilink PPP • Error Detection • Looped Link Detection
    • 565. 565
    • 566. 566
    • 567. 567 Compression • Compression enables higher data throughput across the link. • Different compression schemes are available: – Predictor : checks if the data was already compressed. – Stacker : it looks at the data stream and only sends each type of data once with information about where the type occurs and then the receiving side uses this information to reassemble the data stream. – MPPC (Microsoft Point-to-Point Compression) : allows Cisco routers to compress data with Microsoft clients.
    • 568. 568 PPP Multilink • PPP Multilink provides load balancing over dialer interfaces-including ISDN, synchronous, and asynchronous interfaces. • This can improve throughput and reduce latency between systems by splitting packets and sending fragments over parallel circuits.
    • 569. 569 Error Detection • PPP can take down a link based on the value of what is called LQM (Link Quality Monitor) as it gets the ratio of corrupted packets to the total number of sent packets, and according to a predetermined value, the link can be brought down if it is thought that its performance is beyond limits accepted.
    • 570. 570 Looped Link Detection • PPP can detect looped links (that are sometimes done by Telco companies) using what is called Magic Number. • Every router will have a magic number, and if packets were received having the same router’s magic number, then the link is looped.
    • 571. 571 PPP Configuration Commands • To enable PPP – Router(config-if)#encapsulation ppp • To configure PAP authentication – Router(Config-if)#ppp authentication pap – Router(Config-if)#ppp pap username .. password .. • To configure Compression – Router(Config-if)#compress [predictor|stack| mppc]
    • 572. 572 Frame Relay © 2003, Cisco Systems, Inc. All rights reserved. BCMSN v2.0—2-572
    • 573. 573
    • 574. 574
    • 575. 575 Frame Relay • Frame Relay networks use permanent virtual circuits (PVCs) or switched virtual circuits (SVCs) but most nowadays Frame Relay networks use permanent virtual circuits (PVCs). • The logical path between each pair of routers is called a Virtual Circuit (VC). • VCs share the access link and the frame relay network. • Each VC is committed to a CIR (Committed Information Rate) which is a guarantee by the provider that a particular VC gets at least this much of BW.
    • 576. 576 Video PBX Controller PC Router CPE UNI ISDN dial-up connection or direct connection (V.35, E1, RS232) Desktop & LAN Network access Frame Relay Network Formats packets in frames Port PVC PVC PVC SVC SVC Switch
    • 577. 577 LMI and Encapsulation Types • The LMI is a definition of the messages used between the DTE and the DCE. • The encapsulation defines the headers used by a DTE to communicate some information to the DTE on the other end of a VC. • The switch and its connected router care about using the same LMI; the switch does not care about the encapsulation. The endpoint routers (DTEs) do care about the encapsulation.
    • 578. 578 LMI • The most important LMI message is the LMI status inquiry message. Status messages perform two key functions: – Perform a keepalive function between the DTE and DCE. If the access link has a problem, the absence of keepalive messages implies that the link is down. – Signal whether a PVC is active or inactive. Even though each PVC is predefined, its status can change.
    • 579. 579
    • 580. 580 LAPF • A Frame Relay-connected router encapsulates each Layer 3 packet inside a Frame Relay header and trailer before it is sent out an access link. • The header and trailer are defined by the Link Access Procedure Frame Bearer Services (LAPF) specification. • The LAPF framing provides error detection with an FCS in the trailer, as well as the DLCI, DE, FECN, and BECN fields in the header.
    • 581. 581 LAPF • DTEs use and react to the fields specified by these two types of encapsulation, but Frame Relay switches ignore these fields. Because the frames flow from DTE to DTE, both DTEs must agree to the encapsulation used. • However, each VC can use a different encapsulation. In the configuration, the encapsulation created by Cisco is called cisco, and the other one is called ietf.
    • 582. 582 DLCI Addressing Details • The logical path between a pair of DTEs is called a virtual circuit (VC). • The data-link connection identifier (DLCI) identifies each individual PVC. • When multiple VCs use the same access link, the Frame Relay switches know how to forward the frames to the correct remote sites. The DLCI is the Frame Relay address describing a Virtual Circuit
    • 583. 583 B R R Virtual circuit Router Bridge Frame Relay switch R B FR-network DLCI=16 DLCI=32 DLCI=16 DLCI=16 DLCI=21 DLCI=17 DLCI=17 DLCI=32
    • 584. 584 DLCI Addressing Details • The difference between layer-2 addressing and DLCI addressing is mainly because the fact that the header has a single DLCI field, not both Source and Destination DLCI fields.
    • 585. 585 Global DLCI Addressing • Frame Relay DLCIs are locally significant; this means that the addresses need to be unique only on the local access link. • Global addressing is simply a way of choosing DLCI numbers when planning a Frame Relay network so that working with DLCIs is much easier. • Because local addressing is a fact, global addressing does not change these rules. Global addressing just makes DLCI assignment more obvious.
    • 586. 586
    • 587. 587 Global DLCI Addressing • The final key to global addressing is that the Frame Relay switches actually change the DLCI value before delivering the frame. • The sender treats the DLCI field as a destination address, using the destination’s global DLCI in the header. • The receiver thinks of the DLCI field as the source address, because it contains the global DLCI of the frame’s sender.
    • 588. 588 Layer 3 Addressing • Cisco’s Frame Relay implementation defines three different options for assigning subnets and IP addresses on Frame Relay interfaces: – One subnet containing all Frame Relay DTEs – One subnet per VC – A hybrid of the first two options
    • 589. 589 One Subnet Containing All Frame Relay DTEs • The single-subnet option is typically used when a full mesh of VCs exists. • In a full mesh, each router has a VC to every other router, meaning that each router can send frames directly to every other router
    • 590. 590
    • 591. 591
    • 592. 592 One Subnet Per VC • The single-subnet-per-VC alternative, works better with a partially meshed Frame Relay network.
    • 593. 593
    • 594. 594 Hybrid Terminology • Point-to-point subinterfaces are used when a single VC is considered to be all that is in the group—for instance, between Routers A and D and between Routers A and E. • Multipoint subinterfaces are used when more than two routers are considered to be in the same group— for instance, with Routers A, B, and C.
    • 595. 595
    • 596. 596
    • 597. 597 Frame Relay Address Mapping • Mapping creates a correlation between a Layer-3 address (IP Address) and its corresponding Layer-2 address (DLCI in Frame Relay). • It is used so that after the router receives the packet with the intended IP address could be able to handle it to the right Frame Relay switch (with the appropriate DLCI)
    • 598. 598 Mapping Methods • Mapping can be done either two ways: • Dynamic Mapping – Using the Inverse ARP that is enabled by default on Cisco routers. • Static Mapping – Using the frame-relay map command but you should first disable the inverse arp using the command no frame-relay inverse-arp
    • 599. 599
    • 600. 600
    • 601. 601
    • 602. 602 Integrated Services Digital Network (ISDN) © 2003, Cisco Systems, Inc. All rights reserved. BCMSN v2.0—2-602
    • 603. 603
    • 604. 604
    • 605. 605
    • 606. 606 LAPD & PPP on D and B Channels • LAPD is used as a data-link protocol across an ISDN D channel. • Essentially, a router with an ISDN interface needs to send and receive signaling messages to and from the local ISDN switch to which it is connected. • LAPD provides the data-link protocol that allows delivery of messages across that D channel to the local switch.
    • 607. 607 LAPD & PPP on D and B Channels • The call setup and teardown messages themselves are defined by the Q.931 protocol. So, the local switch can receive a Q.931 call setup request from a router over the LAPD-controlled D channel, and it should react to that Q.931 message by setting up a circuit over the public network.
    • 608. 608 LAPD & PPP on D and B Channels • An ISDN switch often requires some form of authentication with the device connecting to it. • Switches use a free-form decimal value, call the service profile identifier (SPID), to perform authentication. • In short, before any Q.931 call setup messages are accepted, the switch asks for the configured SPID values. If the values match what is configured in the switch, call
    • 609. 609 PRI Encoding and Framing • ISDN PRI in North America is based on a digital T1 circuit. T1 circuits use two different encoding schemes—Alternate Mark Inversion (AMI) and Binary 8 with Zero Substitution (B8ZS). • The two options for framing on T1s are to use either Extended Super Frame (ESF) or the older option—Super Frame (SF). In most cases today, new T1s use ESF.
    • 610. 610 DDR (Dial On Demand Routing) • You can configure DDR in several ways, including Legacy DDR and DDR dialer profiles. • The main difference between the two is that Legacy DDR associates dial details with a physical interface, whereas DDR dialer profiles disassociate the dial configuration from a physical interface, allowing a great deal of flexibility.
    • 611. 611 Legacy DDR Operation 1. Route packets out the interface to be dialed. 2. Determine the subset of the packets that trigger the dialing process. 3. Dial (signal). 4. Determine when the connection is terminated.
    • 612. 612
    • 613. 613 DDR Step 1: Routing Packets Out the Interface to Be Dialed • DDR does not dial until some traffic is directed (routed) out the dial interface. • The router needs to route packets so that they are queued to go out the dial interface. Cisco’s design for DDR defines that the router receives some user-generated traffic and, through normal routing processes, decides to route the traffic out the interface to be dialed. • The router (SanFrancisco) can receive a packet that must be routed out BRI0; routing the packet out BRI0 triggers the Cisco IOS software, causing the dial to occur.
    • 614. 614 DDR Step 2: Determining the Interesting Traffic • Packets that are worthy of causing the device to dial are called interesting packets. • Two different methods can be used to define interesting packets. – In the first method, interesting is defined as all packets of one or more Layer 3 protocols. – The second method allows you to define packets as interesting if they are permitted by an access list.
    • 615. 615 DDR Step 3: Dialing (Signaling) • Defining the phone number to be dialed. • The command is dialer string , where string is the phone number (used when dialing only one site). • The dialer map command maps the different dialer numbers to the equivalent IP addresses of the routers
    • 616. 616 Configuring SPIDs • You might need to configure the Service Profile Identifier (SPID) for one or both B channels, depending on the switch’s expectations. • When the telco switch has configured SPIDs, it might not allow the BRI line to work unless the router announces the correct SPID values to the switch. SPIDs, when used, provide a basic authentication feature.
    • 617. 617 ISDN PRI Configuration 1. Configure the type of ISDN switch to which this router is connected. 2. Configure the T1 or E1 encoding and framing options (controller configuration mode). 3. Configure the T1 or E1 channel range for the DS0 channels used on this PRI (controller configuration mode). 4. Configure any interface settings (for example, PPP encapsulation and IP address) on the interface representing the D channel.
    • 618. 618
    • 619. 619
    • 620. 620 Configuring a T1 or E1 Controller • Your service provider will tell you what encoding and framing to configure on the router. Also, in almost every case, you will use all 24 DS0 channels in the PRI—23 B channels and the D channel.
    • 621. 621 DDR With Dialer Profiles • Dialer profiles pool the physical interfaces so that the router uses any available B channel on any of the BRIs or PRIs in the pool. • Dialer profiles configuration moves most of the DDR interface configuration to a virtual interface called a dialer interface.
    • 622. 622
    • 623. 623
    • 624. With all my best wishes for you to succeed and distinguish in the CCNA International Exam, Keep In touch © 2003, Cisco Systems, Inc. All rights reserved. 624