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
  • Ccna presentation{complete]

    1. 1. © 2003, Cisco Systems, Inc. All rights reserved.
    2. 2. 2
    3. 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. 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. 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. 6 Networking Device Icons
    7. 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. 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. 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. 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. 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. 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. 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. 14 Physical Topologies
    15. 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. 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. 17 Star Topology A star topology connects all cables to a central point of concentration.  
    18. 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. 19 Hierarchical Topology A hierarchical topology is similar to an extended star.
    20. 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. 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. 22 Examples of Data Networks
    23. 23. 23 LANs
    24. 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. 25 Cellular Topology for Wireless
    26. 26. 26 WANs
    27. 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. 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. 29 Bandwidth
    30. 30. 30 Measuring Bandwidth
    31. 31. 31
    32. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 43 OSI Model Analogy Presentation Layer - Source Host Make sure you have the proper directions to disassemble and reassemble the bicycle.
    44. 44. 44 OSI Model Analogy Session Layer - Source Host Call your friend and make sure you have his correct address.
    45. 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. 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. 47 OSI Model Analogy Data Link Layer – Source Host Jamshedpur post office takes possession of the boxes.
    48. 48. 48 OSI Model Analogy Physical Layer - Media The boxes are flown from India to USA.
    49. 49. 49 OSI Model Analogy Data Link Layer - Destination New York post office receives your boxes.
    50. 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. 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. 52 OSI Model Analogy Session Layer - Destination Your friend hangs up because he is done talking to you.
    53. 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. 54 OSI Model Analogy Application Layer - Destination Your friend enjoys riding his new bicycle in New York.
    55. 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. 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. 57
    58. 58. 58
    59. 59. 59 Data Flow Through a Network
    60. 60. 60
    61. 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. 62 Unshielded Twisted Pair (UTP) Cable
    63. 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. 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. 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. 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. 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. 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. 69 Shielded Twisted Pair (STP) Cable
    70. 70. 70 Coaxial Cable
    71. 71. 71 Fiber Optic Cable
    72. 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. 73 Fiber Optic Patch Panels Fiber patch panels similar to the patch panels used with copper cable.
    74. 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. 75 Ethernet Media Connector Requirements
    76. 76. 76 LAN Physical Layer Implementation
    77. 77. 77 Ethernet in the Campus
    78. 78. 78 WAN Physical Layer
    79. 79. 79 WAN Serial Connection Options
    80. 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. 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. 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. 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. 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. 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. 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. 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. 88 Bridges
    89. 89. 89 Bridging Graphic
    90. 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. 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. 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. 93 Switches – MAC Tables
    94. 94. 94 Switches – Parallel Communication
    95. 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. 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. 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. 98
    99. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 112 Sliding Window
    113. 113. 113 Sliding Window with Different Window Sizes
    114. 114. 114 TCP Sequence & Acknowledgement
    115. 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. 116 TCP Segment Format
    117. 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. 118 UDP Segment Format
    119. 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. 120 URL
    121. 121. 121 SNMP – Managed Network
    122. 122. 122
    123. 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. 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. 125
    126. 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. 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. 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. 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. 130 Identifying Address Classes
    131. 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. 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. 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. 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. 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. 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. 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. 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. 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. 140 Finding the Network Address with ANDing By ANDing the Host address of with (its network mask) we obtain the network address of
    141. 141. 141 Network Address
    142. 142. 142 Broadcast Address
    143. 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 B C
    144. 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. 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. 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. 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. 148 The 32-Bit Binary IP Address
    149. 149. 149 Numbers That Show Up In Subnet Masks (Memorize Them!)
    150. 150. 150 Addressing with Subnetworks
    151. 151. 151 Obtaining an Internet Address
    152. 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. 153 SIEMENS NI XDORF SIEMENS NIXDORF Host A Host B IP Address: HW Address: 080020021545 ARP Reply ARP Request - Broadcast to all hosts „What is the hardware address for IP address“ SI EMENS NI XDORF Fig. 32 How does ARP work? (TI1332EU02TI_0004 The Network Layer, 47) ARP (Address Resolution Protocol)
    154. 154. 154 Fig. 33 The ARP command (TI1332EU02TI_0004 The Network Layer, 47)
    155. 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. 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. 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. 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. 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. 160
    161. 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. 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. 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. 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. 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. 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. 167 Internal Components of a 2600 Router
    168. 168. 168 External Components of a 2600 Router
    169. 169. 169 External Connections
    170. 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. 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. 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. 173 Computer/Terminal Console Connection
    174. 174. 174 Modem Connection to Console/Aux Port
    175. 175. 175 HyperTerminal Session Properties
    176. 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. 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. 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. 179 Router Command Line Interface
    180. 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. 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. 182 IOS File System Overview
    183. 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. 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. 185 Step in Router Initialization
    186. 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. 187 Enhanced Cisco IOS Commands
    188. 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. 189
    190. 190. 190
    191. 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. 192 Overview of Router Modes
    193. 193. 193 Router Modes
    194. 194. 194 User Mode Commands
    195. 195. 195 Privileged Mode Commands NOTE: There are many more commands available in privileged mode.
    196. 196. 196 Specific Configuration Modes
    197. 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. 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. 199 Setting the Clock with Help
    200. 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. 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. 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. 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 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 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. 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. 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. 206
    207. 207. 207
    208. 208. 208
    209. 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. 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. 211 Ethernet Technologies Mapped to the OSI Model
    212. 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. 213 Ethernet and IEEE Frame Formats are Very Similar
    214. 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. 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. 216 CSMA/CD Graphic
    217. 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. 218
    219. 219. Hierarchical Addressing Using Variable-Length Subnet Masks © 2003, Cisco Systems, Inc. All rights reserved. 219
    220. 220. 220 Prefix Length and Network Mask Range of Addresses: through • 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 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. 221 Implementing VLSM
    222. 222. 222 Range Of Addresses for VLSM
    223. 223. 223 Breakdown Address Space for Largest Subnet
    224. 224. 224 for Ethernets at Remote Sites
    225. 225. 225 Address Space for Serial Subnets
    226. 226. 226 Calculating VLSM: Binary
    227. 227. Route Summarization and Classless Interdomain Routing © 2003, Cisco Systems, Inc. All rights reserved. 227
    228. 228. 228 What Is Route Summarization?
    229. 229. 229 Summarizing Within an Octet
    230. 230. 230 Summarizing Addresses in a VLSM-Designed Network
    231. 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. 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. 233 CIDR Example
    234. 234. 234
    235. 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. 236
    237. 237. 237
    238. 238. 238
    239. 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 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. 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 [next-hop-address | outgoing interface] This is sometimes referred to as a “Quad-Zero” route. Example using next hop address: Router(config)#ip route Example using the exit interface: Router(config)#ip route s0/0
    241. 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. 242
    243. 243. 243 Path Determination Graphic
    244. 244. 244 Router Router Router Router Router What is an optimal route ? What is an optimal route ? Switch Switch Routing Protocol
    245. 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. 246
    247. 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. 248
    249. 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. 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. 251 IGP and EGP An autonomous system is a network or set of networks under common administrative control, such as the domain.
    252. 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. 253 Distance Vector Routing Concepts
    254. 254. 254 2 Hops 1 Hop1 Hop Destination 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 Distance Vector Routing (DVR)
    255. 255. 255 Routing Tables Graphic
    256. 256. 256 Distance Vector Topology Changes
    257. 257. 257 Router Metric Components
    258. 258. 258 Router CRouter A Router D Router B 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. 259 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 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. 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. 261 RIP Characteristics
    262. 262. 262 Router A Port 2 Port 2 Port 1 Port 1 RIP-1: RIP-1: RIP-1: 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. 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 The network numbers are based on the network class addresses, not subnet addresses or individual host addresses.
    264. 264. 264 Configuring RIP Example
    265. 265. 265 Verifying RIP Configuration
    266. 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. 267 Problem: Routing LoopsRouting loops can occur when inconsistent routing tables are not updated due to slow convergence in a changing network.
    268. 268. 268 Problem: Counting to Infinity
    269. 269. 269 Solution: Define a Maximum
    270. 270. 270 Solution: Split Horizon
    271. 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. 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. 273 Triggered Updates Graphic
    274. 274. 274 Solution: Holddown Timers
    275. 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. 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. 277 Configuring IGRP
    278. 278. 278 Routing Metrics Graphics
    279. 279. 279 Link State Concepts
    280. 280. 280 Link State Topology Changes
    281. 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) state packet SPF... shortest path first
    282. 282. 282 Link State Concerns
    283. 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. 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. 285 Link State Routing
    286. 286. 286 Comparing Routing Methods
    287. 287. OSPF (Open Shortest Path First) Protocol © 2003, Cisco Systems, Inc. All rights reserved. 287
    288. 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. 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. 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. 291 OSPF Terminology The next several slides explain various OSPF terms -one per slide.
    292. 292. 292 OSPF Term: Link
    293. 293. 293 OSPF Term: Link State
    294. 294. 294 OSPF Term: Area
    295. 295. 295 OSPF Term: Link Cost
    296. 296. 296 OSPF Term: Forwarding Database
    297. 297. 297 OSPF Term: Adjacencies Database
    298. 298. 298 OSPF Terms: DR & BDR
    299. 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. 300 OSPF Areas
    301. 301. 301 Area Terminology
    302. 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. 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. 304
    305. 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. 306 OSPF Packet Types
    307. 307. 307 OSPF Packet Header Format
    308. 308. 308 Neighborship
    309. 309. 309 Establishing Bidirectional Communication
    310. 310. 310 Establishing Bidirectional Communication (Cont.)
    311. 311. 311 Establishing Bidirectional Communication (Cont.)
    312. 312. 312 Establishing Bidirectional Communication
    313. 313. 313 Discovering the Network Routes
    314. 314. 314 Discovering the Network Routes
    315. 315. 315 Adding the Link-State Entries
    316. 316. 316 Adding the Link-State Entries (Cont.)
    317. 317. 317 Adding the Link-State Entries
    318. 318. 318 Maintaining Routing Information • Router A notifies all OSPF DRs on
    319. 319. 319 Maintaining Routing Information (Cont.) • Router A notifies all OSPF DRs on • DR notifies others on
    320. 320. 320 Maintaining Routing Information (Cont.) • Router A notifies all OSPF DRs on • DR notifies others on
    321. 321. 321 Maintaining Routing Information • Router A notifies all OSPF DRs on • DR notifies others on
    322. 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. 323 Configuring OSPF on Internal Routers of a Single Area
    324. 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. 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. 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 is subnetted, 2 subnets O [110/10] via, 00:00:50, Ethernet0
    327. 327. 327 The show ip ospf interface Command RouterA# show ip ospf interface e0 Ethernet0 is up, line protocol is up Internet Address, Area 0 Process ID 1, Router ID, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State DROTHER, Priority 1 Designated Router (ID), Interface address Backup Designated router (ID), Interface address 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 (Designated Router) Suppress hello for 0 neighbor(s)
    328. 328. 328 The show ip ospf neighbor Command RouterB# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 1 FULL/BDR 00:00:31 Ethernet0 1 FULL/- 00:00:38 Serial0
    329. 329. 329 show ip protocol show ip route
    330. 330. 330 show ip ospf neighbor detail show ip ospf database
    331. 331. 331 OSPF Network Types - 1
    332. 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
    333. 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 • Packets from DR to all other routers use
    334. 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. 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. 336 OSPF Network Types - 2
    337. 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 area 0 from Serial1 OSPF: End of hello processing OSPF: Build router LSA for area 0, router ID OSPF: Rcv DBD from on Serial1 seq 0x20C4 opt 0x2 flag 0x7 len 32 state INIT OSPF: 2 Way Communication to on Serial1, state 2WAY OSPF: Send DBD to on Serial1 seq 0x167F opt 0x2 flag 0x7 len 32 OSPF: NBR Negotiation Done. We are the SLAVE OSPF: Send DBD to on Serial1 seq 0x20C4 opt 0x2 flag 0x2 len 72
    338. 338. 338 Creation of Adjacencies (Cont.) RouterA# debug ip ospf adj Ethernet interface coming up: Election OSPF: 2 Way Communication to on Ethernet0, state 2WAY OSPF: end of Wait on interface Ethernet0 OSPF: DR/BDR election on Ethernet0 OSPF: Elect BDR OSPF: Elect DR DR: (Id) BDR: (Id) OSPF: Send DBD to on Ethernet0 seq 0x546 opt 0x2 flag 0x7 len 32 <…> OSPF: DR/BDR election on Ethernet0 OSPF: Elect BDR OSPF: Elect DR DR: (Id) BDR: (Id)
    339. 339. 339
    340. 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. 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. 342 EIGRP & IGRP Metric Calculation
    343. 343. 343 Comparing EIGRP with IGRP
    344. 344. 344 Comparing EIGRP with IGRP
    345. 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. 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. 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. 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. 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
    350. 350. 350 Default Hello Intervals and Hold Times for EIGRP
    351. 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. 352 FS Route Selection Rules
    353. 353. 353 DUAL Example
    354. 354. 354 Configuring EIGRP
    355. 355. 355
    356. 356. 356
    357. 357. 357
    358. 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. 359
    360. 360. 360 show ip eigrp topology show ip eigrp topology [active | pending | successors]
    361. 361. 361 show ip eigrp topology all-links show ip eigrp traffic
    362. 362. 362 Administrative Distances
    363. 363. 363 Classful and Classless Routing Protocols
    364. 364. 364
    365. 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. 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. 367 ACLs Filter Traffic Graphic
    368. 368. 368 How ACLs Filter Traffic
    369. 369. 369 One List per Port, per Destination, per Protocol...
    370. 370. 370 How ACLs work.
    371. 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. 372 The access-list command
    373. 373. 373 The ip access-group command { in | out }
    374. 374. 374 ACL Example
    375. 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. 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. 377 Wildcard Mask Example #1
    378. 378. 378 Wildcard Mask Example #2
    379. 379. 379 Wildcard Mask Example #3
    380. 380. 380 Wildcard Mask Example #4 - Even IPs
    381. 381. 381 Wildcard Mask Example #5 - Odd IP#s
    382. 382. 382 The any and host Keywords
    383. 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. 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 (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. 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. 386 Extended ACL Syntax