Chapter3 frame relay

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  • Graphic 3.1.1.1 (frame relay)
  • Graphic 3.1.2.1 Graphic 3.1.2.2
  • Graphic 3.1.3.1
  • Graphic 3.1.4.1 Graphic 3.1.4.2
  • Graphic 3.1.4.1 Graphic 3.1.4.2
  • Graphic 3.1.5.4
  • Graphic 3.1.5.4
  • Graphic 3.2.2.1
  • Graphic 3.3.1.1
  • Graphic 3.3.2.1 & 3.3.2.2
  • Graphic 3.3.3.1
  • Graphic 3.4.1.2
  • Graphic 3.4.2.1
  • Graphic 3.4.2.1
  • Graphic 3.4.2.1
  • Graphic 3.4.2.1
  • Graphic 3.4.3.1
  • Graphic 3.4.3.1
  • Chapter3 frame relay

    1. 1. Frame Relay Accessing the WAN – Chapter 3ITE I Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1
    2. 2. Historical Background  Frame Relay is a high-performance WAN protocol that operates at the physical and data link layers of the OSI model.  Eric Scace, an engineer at Sprint International, invented Frame Relay as a simpler version of the X.25 protocol to use across ISDN interfaces.  Network providers commonly implement Frame Relay for voice and data as an encapsulation technique, used between LANs over a WAN. Each end user gets a private line (or leased line) to a Frame Relay node.  Frame Relay has become one of the most extensively used WAN protocols, primarily because it is inexpensive compared to dedicated lines.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 2
    3. 3. Introducing Frame Relay  Frame Relay has become the most widely used WAN technology in the world primarily because of its price and flexibility.  Frame Relay reduces network costs by using less equipment, less complexity, and an easier implementation. Moreover, Frame Relay provides greater bandwidth, reliability, and resiliency than private or leased lines.  With increasing globalization and the growth of one- to-many branch office topologies, Frame Relay offers simpler network architecture at a lower cost of ownership.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 3
    4. 4. Describe the Fundamental Concepts of Frame Relay Technology  Describe how Frame Relay is used to provide WAN services to the EnterpriseITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 4
    5. 5. Describe the Fundamental Concepts of Frame Relay Technology  Frame Relay OperationITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 5
    6. 6. Describe the Fundamental Concepts of Frame Relay Technology  Virtual circuit (VC) - connection through a Frame Relay network between two DTEs; maybe SVCs or PVCs  VCs are identified by DLCIs. DLCI values are assigned by the service provider; DLCIs have local significance  DLCIs 0 to 15 and 1008 to 1023 are reserved for special purposes.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 6
    7. 7. Describe the Fundamental Concepts of Frame Relay TechnologyITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 7
    8. 8. Describe the Fundamental Concepts of Frame Relay Technology  Describe the types of topologies that are used for implementing Frame Relay in different environments In mesh networks, total VCs required is [n(n-1)/2]ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 8
    9. 9. Describe the Fundamental Concepts of Frame Relay Technology  Frame Relay Address Mapping  Dynamic address mapping - relies on Inverse ARP (IARP) to resolve a next hop network protocol address to a local DLCI value.  On Cisco routers, Inverse ARP is enabled by default for all protocols  One can choose to override dynamic Inverse ARP mapping by supplying a manual static mapping for the next hop protocol address to a local DLCI.  You cannot use Inverse ARP and a frame-relay map statement for the same DLCI and protocol.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 9
    10. 10. Describe the Fundamental Concepts of Frame Relay Technology  LMI - a keepalive mechanism that provides status information about FR connections between the router (DTE) and the FR switch (DCE)  Do not confuse LMI with encapsulation. LMI defines messages used between the DTE and the DCE. Encapsulation defines the headers used by a DTE to communicate information to the DTE at the other end of a VC.  Three types of LMIs are supported by Cisco routers: Cisco, Ansi and q933a.  Starting with Cisco IOS 11.2, the default LMI autosense feature detects the LMI type supported by the directly connected Frame Relay switch.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 10
    11. 11. Describe the Fundamental Concepts of Frame Relay Technology  LMI status messages combined with Inverse ARP messages allow a router to associate network layer and data link layer addresses.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 11
    12. 12. Configure a Basic Frame Relay PVC  Configure a basic Frame Relay PVC on a router serial interface  Verify encapsulation through sh int serial 0/0/0ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 12
    13. 13. Configure a Basic Frame Relay PVC  Configure a static Frame Relay map  Frame Relay is an NBMA network which does not support broadcast traffic, using the broadcast keyword is a simplified way to forward routing updates.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 13
    14. 14. Describe Advanced Concepts of Frame Relay Technology Split Horizon prohibits routing updates received on an interface from exiting that same interface.  Using a hub and spoke topology, the split horizon rule reduces the chance of a routing loop with distance vector routing protocols.  It prevents a routing update received on an interface from being forwarded through the same interface.  If the Central router learns about Network X from Branch A, that update is learned via S0/0.  According to the split horizon rule, Central could not update Branch B or Branch C about Network X.  This is because that update would be sent out the S0/0 interface, which is the same interface that received the update.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 14
    15. 15. Describe Advanced Concepts of Frame Relay Technology  Frame Relay can allow customers to dynamically access this extra bandwidth and "burst" over their CIR for free.•The duration of a bursttransmission should be short.•BE is the term used to describethe bandwidth available abovethe CBIR.•Unlike the CBIR, it is notnegotiated.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 15
    16. 16. Describe Advanced Concepts of Frame Relay Technology • Forward Explicit Congestion Notification (FECN) – When a Frame Relay switch recognizes congestion in the network, it sends an FECN packet to the destination device. – This indicates that congestion has occurred. • Backward Explicit Congestion Notification (BECN) – When a Frame Relay switch recognizes congestion in the network, it sends a BECN packet to the source router. – This instructs the router to reduce the rate at which it is sending packets.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 16
    17. 17. Configure an Advanced Frame Relay PVC  Explain the steps to configure point-to-point subinterfaces on a physical interfaceITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 17
    18. 18. Configure an Advanced Frame Relay PVC  Describe the commands used for verifying Frame Relay operationITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 18
    19. 19. Configure an Advanced Frame Relay PVC  The show frame-relay lmi command displays LMI traffic statistics showing the number of status messages exchanged between the local router and the Frame Relay switch.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 19
    20. 20. Configure an Advanced Frame Relay PVC • The show frame-relay pvc command displays the status of each configured connection, as well as traffic statistics. • This command is also useful for viewing the number of BECN and FECN packets received by the router. • The command show frame-relay pvc shows the status of all PVCs configured on the router.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 20
    21. 21. Configure an Advanced Frame Relay PVC • To clear dynamically created Frame Relay maps, which are created using Inverse ARP, use the clear frame-relay-inarp command.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 21
    22. 22. Configure an Advanced Frame Relay PVC  Use the debug frame-relay lmi command to determine whether the router and the Frame Relay switch are sending and receiving LMI packets properly.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 22
    23. 23. Configure an Advanced Frame Relay PVC  The possible values of the status field are as follows:  0x0 – Added/inactive means that the switch has this DLCI programmed but for some reason it is not usable. The reason could possibly be the other end of the PVC is down.  0x2 – Added/active means the Frame Relay switch has the DLCI and everything is operational.  0x4 – Deleted means that the Frame Relay switch does not have this DLCI programmed for the router, but that it was programmed at some point in the past. This could also be caused by the DLCIs being reversed on the router, or by the PVC being deleted by the service provider in the Frame Relay cloud.ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 23
    24. 24. Summary  Frame relay is the most widely used WAN technology because it: –Provides greater bandwidth than leased line –Reduces cost because it uses less equipment –Easy to implement  Frame relay is associated with layer 2 of the OSI model and encapsulates data packets in a frame relay frame  Frame relay is configured on virtual circuits –These virtual circuits may be identified by a DLCI  Frame relay uses inverse ARP to map DLCI to IP addressesITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 24
    25. 25. Summary  Configuring frame relay requires –Enable frame relay encapsulation –Configuring either static or dynamic mapping –Considering split horizon problems that develop when multiple VCs are placed on a single physical interface  Factor affecting frame relay configuration –How service provider has their charging scheme set up  Frame relay flow control –DE –FECN –BECNITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 25
    26. 26. Summary  The following commands can be used to help verify frame relay configuration –Show interfaces –Show frame-relay lmi –Show frame-relay pvc ### –Show frame-relay map  Use the following command to help troubleshoot a frame relay configuration –Debug frame-relay lmiITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 26
    27. 27. ITE 1 Chapter 6 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 27

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