CCNA PPP and Frame Relay
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CCNA PPP and Frame Relay

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CCNA PPP and Frame Relay CCNA PPP and Frame Relay Presentation Transcript

  • CCNA Guide to Cisco Networking Fundamentals Chapter 11 PPP and Frame Relay
  • Objectives
    • Describe PPP encapsulation
    • Configure PPP encapsulation and its options
    • Describe and enable PPP multilink
    • Understand Frame Relay standards and equipment
    CCNA Guide to Cisco Networking Fundamentals
  • Objectives (continued)
    • Describe the role of virtual circuits and performance parameters in Frame Relay
    • Understand the Frame Relay topologies
    • Understand the difference between multipoint and point-to-point configurations
    • Configure and monitor Frame Relay
    CCNA Guide to Cisco Networking Fundamentals View slide
  • PPP
    • PPP
      • Internet standard protocol defined in RFCs 2153 and 1661
      • Provide point-to-point, router-to-router, host-to-router, and host-to-host connections
      • Considered a peer technology based on its point-to-point physical configuration
      • Commonly used over dial-up or leased lines to provide connections into IP networks
    • Serial Line Internet Protocol (SLIP) was the predecessor to PPP
    CCNA Guide to Cisco Networking Fundamentals View slide
  • PPP (continued)
    • PPP can be used over several different physical interfaces, including the following:
      • Asynchronous serial
      • ISDN synchronous serial
      • High-Speed Serial Interface (HSSI)
    CCNA Guide to Cisco Networking Fundamentals
  • PPP in the Protocol Stack
    • You can use PPP over both asynchronous and synchronous connections
      • At the Physical layer of the OSI reference model
    • Link Control Protocol (LCP)
      • Used at the Data Link layer to establish, configure, and test the connection
    • Network Control Protocols (NCPs)
      • Allow the simultaneous use of multiple Network layer protocols and are required for each protocol that uses PPP
    CCNA Guide to Cisco Networking Fundamentals
  • PPP in the Protocol Stack (continued) CCNA Guide to Cisco Networking Fundamentals
  • Frame Format
    • PPP is based on the High-Level Data Link Control (HDLC) protocol
    • The difference between PPP frames and HDLC frames is that PPP frames contain protocol and Link Control Protocol (LCP) fields
    • LCP
      • Described in RFCs 1548, 1570, 1661, 2153, and 2484
      • Describes PPP organization and methodology, including basic LCP extensions
    CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Frame Format (continued)
    • LCP field of the PPP packet can contain many different pieces of information, including the following:
      • Asynchronous character map
      • Maximum receive unit size
      • Compression
      • Authentication
      • Magic number
      • Link Quality Monitoring (LQM)
      • Multilink
    CCNA Guide to Cisco Networking Fundamentals
  • Frame Format (continued)
    • LCP link configuration process
      • Modifies and enhances the default characteristics of a PPP connection
    • Includes the following actions:
      • Link establishment
      • Authentication (optional)
      • Link-quality determination (optional)
      • Network layer protocol configuration negotiation
      • Link termination
    CCNA Guide to Cisco Networking Fundamentals
  • Establishing PPP Communications
    • Involves the following actions:
      • Link establishment
      • Optional authentication
      • Network layer protocol configuration negotiation
    • The link establishment phase involves the configuration and testing of the data link
    • The authentication process can use two authentication types with PPP connections: PAP and CHAP
    CCNA Guide to Cisco Networking Fundamentals
  • Establishing PPP Communications (continued)
    • PPP is an encapsulation type for serial interface communications
      • To configure a PPP connection, you must access the interface configuration mode for the specific interface you want to configure
    • After LCP has finished negotiating the configuration parameters
      • Network layer protocols can be configured individually by the appropriate NCP
    CCNA Guide to Cisco Networking Fundamentals
  • Establishing PPP Communications (continued) CCNA Guide to Cisco Networking Fundamentals
  • Establishing PPP Communications (continued)
    • Configuring PPP Authentication
      • Using authentication with PPP connections is optional
      • You must specifically configure PPP authentication on each PPP host in order for the host to use it
      • You can choose to enable CHAP, PAP, or both on your PPP connection, in either order
    CCNA Guide to Cisco Networking Fundamentals
  • Establishing PPP Communications (continued)
    • Once you set the authentication type
      • You must still configure a username and password for the authentication
    • You must exit interface configuration mode and enter global configuration mode
      • Type username followed by the host name of the remote router
      • Then type password followed by the password for that connection
    • Confirming PPP Communications
      • With the show interface command
    CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Establishing PPP Communications (continued) CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Standards and Equipment
    • Frame Relay
      • A packet switching and encapsulation technology that functions at the Physical and Data Link layers of the OSI reference model
      • A communications technique for sending data over high-speed digital connections
    • ITU-T and ANSI define Frame Relay
      • As a connection between the data terminal equipment (DTE) and the data communications equipment (DCE)
    CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Standards and Equipment (continued) CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Standards and Equipment (continued)
    • The physical equipment that is used on a network may vary from one organization to another
    • Some routers have built-in cards that allow them to make WAN connections
    CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Standards and Equipment (continued) CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Standards and Equipment (continued)
    • Frame Relay access device (FRAD)
      • Network device that connects to the Frame Relay switch
      • Also known as Frame Relay assembler/disassembler
    • Frame Relay network device (FRND)
      • The Frame Relay switch
    CCNA Guide to Cisco Networking Fundamentals
  • Virtual Circuits
    • You can use Frame Relay with nearly any serial interface
      • Operates by multiplexing
    • Frame Relay separates each data stream into logical (software-maintained) connections
      • Called virtual circuits
      • Which carry the data transferred on the connection
    • Two types of virtual circuits
      • Switched virtual circuits (SVC)
      • Permanent virtual circuits (PVC)
    CCNA Guide to Cisco Networking Fundamentals
  • DLCI
    • Frame relay connections identify virtual circuits by Data Link Connection Identifier (DLCI) numbers
    • A DLCI number associates an IP address with a specific virtual circuit
    • DLCI numbers have only local significance
    • DLCI numbers are usually assigned by the Frame Relay provider
      • Most likely not the same on either side of the Frame Relay switch
    CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Map
    • Frame Relay map
      • A table in RAM that defines the remote interface to which a specific DLCI number is mapped
    • The definition will contain a DLCI number and an interface identifier
      • Which is typically a remote IP address
    • The Frame Relay map can be built automatically or statically depending on the Frame Relay topology
    CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Map (continued)
    • Subinterfaces
      • Virtual interfaces associated with a physical interface
      • Created by referencing the physical interface followed by a period and a decimal number
    • For the purposes of routing, however, subinterfaces are treated as physical interfaces
    • With subinterfaces, the cost of implementing multiple Frame Relay virtual circuits is reduced
      • Because only one port is required on the router
    CCNA Guide to Cisco Networking Fundamentals
  • LMI
    • LMI basically extended the functionality of Frame Relay by:
      • Making the DLCIs globally significant rather than locally significant
      • Creating a signaling mechanism between the router and the Frame Relay switch, which could report on the status of the link
      • Supporting multicasting
    • Providing DLCI numbers that are globally significant makes automatic configuration of the Frame Relay map possible
    CCNA Guide to Cisco Networking Fundamentals
  • LMI (continued)
    • LMI uses keepalive packets to verify the Frame Relay link and to ensure the flow of data
    • Each virtual circuit, represented by its DLCI number, can have one of three connection states:
      • Active
      • Inactive
      • Deleted
    • The Frame Relay switch reports this status information to the Frame Relay map on the local router
    CCNA Guide to Cisco Networking Fundamentals
  • Inverse ARP
    • In multipoint configurations
      • Routers use the protocol Inverse ARP to send a query using the DLCI number to find a remote IP address
    • As other routers respond to the Inverse ARP queries, the local router can build its Frame Relay map automatically
    • To maintain the Frame Relay map, routers exchange Inverse ARP messages every 60 seconds by default
    CCNA Guide to Cisco Networking Fundamentals
  • Encapsulation Types
    • LMI has several different protocol encapsulation types that it can use for management communications
    • Cisco routers support these types of LMI encapsulation:
      • cisco
      • ansi
      • q933a
    • Cisco routers (using IOS Release 11.2 or later) can “autosense” the LMI type used by the Frame Relay switch
    CCNA Guide to Cisco Networking Fundamentals
  • Encapsulation Types (continued)
    • The basic LMI type has three information elements: report type, keepalive, and PVC status
    • Information concerning the status of the virtual circuit:
      • New
      • Active
      • Receiver not ready
      • Minimum bandwidth
      • Global addressing
      • Multicasting
      • Provider-Initiated Status Update
    CCNA Guide to Cisco Networking Fundamentals
  • Encapsulation Types (continued)
    • Split horizon
      • Routing technique that reduces the chance of routing loops on a network
      • Prevents routing update information received on one physical interface from being rebroadcast to other devices through that same physical interface
      • People also refer to this rule as nonbroadcast multiaccess (NBMA)
      • Can cause problems for Frame Relay routing updates
    • The best solution is to configure separate point-to-point subinterfaces for each virtual connection
    CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Performance Parameters
    • Service contract specifies parameters by which the connection is expected to function:
      • Access rate
      • Committed Information Rate (CIR)
      • Committed Burst Size (CBS)
      • Excess Burst Size (EBS)
      • Oversubscription
    CCNA Guide to Cisco Networking Fundamentals
  • Congestion
    • Frame Relay switches attempt to control congestion on the network
    • When the Frame Relay switch recognizes congestion
      • Sends a forward explicit congestion notification (FECN) message to the destination router
    • In addition, the switch sends a backward explicit congestion notification (BECN) message to the transmitting, or source, router
    CCNA Guide to Cisco Networking Fundamentals
  • Frame Format CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Topologies
    • Frame Relay can use many different WAN topologies:
      • Peer (point-to-point)
      • Star (hub and spoke)
      • Partial mesh
      • Full mesh physical
    CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Configuration
    • In this section, you will learn how to configure Frame Relay over serial interfaces
      • Using IP as the Network layer protocol
    CCNA Guide to Cisco Networking Fundamentals
  • Basic Multipoint Configuration with Two Routers
    • LMI will notify the router about the available DLCI numbers
      • Inverse ARP will build the Frame Relay map dynamically
    CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Basic Multipoint Configuration with Two Routers (continued) CCNA Guide to Cisco Networking Fundamentals
  • Multipoint Configuration Using a Subinterface
    • The Frame Relay map will have to be built statically on RouterA
      • To configure a multipoint subinterface, you map it to multiple remote routers using the same subnet mask, but different DLCI numbers
    CCNA Guide to Cisco Networking Fundamentals
  • Multipoint Configuration Using a Subinterface (continued) CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Point-to-Point Configuration Using Subinterfaces
    • Point-to-point Frame Relay configurations do not support Inverse ARP
    • You will have to configure each subnet separately
      • Use the frame-relay interface-dlci command to associate the DLCI numbers with a specific subinterface
    CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Frame Relay Static Mapping
    • Sometimes you have to define the DLCI numbers manually
      • This is called making a static address to DLCI Frame Relay map
    • You statically configure your DLCI entries in the following situations:
      • The remote router does not support Inverse ARP
      • You need to assign specific subinterfaces to specific DLCI connections
      • You want to reduce broadcast traffic
      • You are configuring OSPF over Frame Relay
    CCNA Guide to Cisco Networking Fundamentals
  • Non-Cisco Routers
    • Non-Cisco routers use a different Frame Relay encapsulation than Cisco routers
    • If you are configuring Cisco routers to connect to other Cisco routers
      • They will automatically use the Cisco Frame Relay encapsulation
    • If you are connecting a Cisco router to a non-Cisco router, you must specify ietf Frame Relay encapsulation using the following command:
      • RouterA(config-if)#encapsulation frame-relay ietf
    CCNA Guide to Cisco Networking Fundamentals
  • Keepalive Configuration
    • By default, keepalive packets are sent out every 10 seconds to the Frame Relay switch
    • You can change the keepalive period by typing keepalive followed by the time in seconds
      • RouterA(config-if)#keepalive 15
    CCNA Guide to Cisco Networking Fundamentals
  • Monitoring Frame Relay
    • You can check your Frame Relay configuration by using show commands
      • These commands allow you to verify that the commands you previously entered produced the desired effect on your router
    • The most common show commands for monitoring Frame Relay operation are:
        • show interface
        • show frame-relay pvc
        • show frame-relay map
        • show frame-relay lmi
    CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • CCNA Guide to Cisco Networking Fundamentals
  • Summary
    • Many WAN connectivity options are available for modern networks, including digital lines, Frame Relay, and analog modems
    • The Point-to-Point Protocol (PPP) is the most widely used WAN protocol today
    • PPP provides link establishment, quality determination, Network layer protocol encapsulation, and link termination services
    • Frame relay is a flexible WAN technology that can be used to connect two geographically separate LANs
    CCNA Guide to Cisco Networking Fundamentals
  • Summary (continued)
    • Frame relay is both a service and type of encapsulation
    • Service parameters for Frame Relay include the access rate, Committed Information Rate (CIR), Committed Burst Size (CBS), and Excess Burst Size (EBS)
    • Frame relay connections employ virtual circuits that can be either permanent or switched
    • Virtual circuit connections across Frame Relay connections are defined by Data Link Connection Identifier (DLCI) numbers
    CCNA Guide to Cisco Networking Fundamentals
  • Summary (continued)
    • Most Frame Relay providers support LMI, which allows Frame Relay maps to be dynamically created via Inverse ARP
    • Static mappings of DLCI numbers to remote IP addresses can be configured when routers do not support Inverse ARP
    • Inverse ARP is not enabled on point-to-point links because only one path is available
    • Frame relay circuits can be established over serial interfaces or subinterfaces on Cisco routers
    CCNA Guide to Cisco Networking Fundamentals