Lab 9.1.4.1: Excessive Traffic Load Dial Backup

 

Objective:

Implement a standby ISDN DDR system for your Frame Relay network between Orlando and Atlanta for on-demand bandwidth when the Frame Relay interface is overloaded.

Scenario:

You have just installed an ISDN line to be used as standby reserve bandwidth your Frame Relay connection between the Atlanta and Orlando office. Configure DDR on the BRI interface of the Orlando router. Configure Frame Relay on the serial interfaces connecting to the Frame Relay network. Configure parallel static routes so that when both links are up traffic will load balance between the two links.

Lab Tasks:

  1. Cable the lab as shown in the diagram. Use the Adtran Atlas 550 as your ISDN and Frame Relay networks.
  2. First configure your ISDN BRI lines. Assign the appropriate SPIDs and dialer maps to implement DDR. Be sure to configure the following items:

    • PPP encapsulation
    • CHAP authentication
    • ISDN Spid numbers
    • Idle timeouts
    • Map statements

    Test your DDR configuration to make sure it is functional.

  3. Next, setup your Frame Relay network. Configure Frame Relay encapsulation on your serial links. Use the DLCIs specified in the above diagram.

    Use ANSI as your LMI type.

    Use sub-interfaces. Configure the appropriate IP addresses.

    Test your Frame Relay configuration to make sure it is functional.

  4. When you are satisfied that both components are functional, turn on the standby dial feature on the Orlando Frame Relay interface. This will enable the BRI line to use DDR when the Frame Relay link is overloaded.
    • On the Orlando router:

    Orlando(config)#int s0/0
    Orlando(config-if)#backup interface bri0/0
    Orlando(config-if)#backup load 2 1

  5. Now install your parallel static routes:


    Note: If you have a WIC 2T card, add the command bandwidth 128 to the serial interface. This will make the interface easier to load.
    • For the Orlando router, you need default routes that will point to both the Frame Relay and ISDN interfaces.

    What commands would you use to install these routes?

    • For the Atlanta router, you need a route to Orlando's Ethernet (192.168.1.0) that will point to both the Frame Relay and ISDN interfaces.

    What commands would you use to install these routes?

  6. At this point, your Frame Relay network should be up. From the Orlando router, look at your routing table. What is the next hop address of your default route?

    In what state is your BRI interface?


  7. Check the serial interface to verfiy the backup interface load levels with the show interface s0/0 command.

    What load level is the back setup to kick in at?

  8. Create a large amount of traffic destined for the Atlanta router. Create a telnet session into the Orlando router from the Atlanta router. This will allow you to keep the Orlando console free to see console messages.

    From the telnet session to Orlando do an extended ping using very large packet sizes. This will saturate the link and cause the backup to kick in. Make sure you create enough of them to keep the traffic going for a while. This will give you more time to observe what is happening.

    Orlando#ping
    Protocol [ip]:
    Target IP address: 192.168.2.1
    Repeat count [5]: 500
    Datagram size [100]: 1460
    Timeout in seconds [2]:
    Extended commands [n]:
    Sweep range of sizes [n]:
    Type escape sequence to abort.
    Sending 500, 1460-byte ICMP Echos to 192.168.2.1, timeout is 2 seconds:
    !!!!!!!!!!!!!!!!

  9. Watch your console session on the Orlando router to see what happens to the BRI interface.

    What happened?



    Look at the routing table on the Orlando router. What do you notice?

    Look at the status of the dial backup link with the show backup command.

    What do you see?


  10. Stop your ping.

    What happens?


  11. When everything is back to normal, check the status of the dial backup link using the show backup command.