Lab 5.5.4: Default Routes - Redistribution - Passive Interfaces

Objectives:

  • Ensure successful routing in a DDR environment by adding default routes and redistributing remote routes into the core of our network.

Scenario:

You have just installed a new branch office that will use DDR to dial into your central site. The next step is to configure routing so the branch office can successfully communicate with the central site using TCP/IP. You will need to install a default route at the branch office pointing back at the central site. At the central site you will need to add a static route for the branch office Ethernet network pointing back at the branch office router. To ensure that the branch office can communicate with the rest of the central site, redistribute the static route to the core network running IGRP.

Notes: 

Lab Tasks:

  1. Cable the lab as shown in the diagram. Use the Adtran Atlas 550 to simulate the ISDN network.
  2. Configure the branch office router and the central site router so they will dial each other when interesting traffic is present. Use PPP encapsulation and CHAP authentication. Verify that each site can dial the other site successfully.
  3. Because the branch office router is a stub network, define a default route that will point back at the central site.

    What is the command to add a default route to point back at the central site:

    Add the command to the branch office router.

    Ping the core router (192.168.2.2). Can you ping it?

    Does your BRI link come up?

    What is wrong?


  4. There is only one network at the branch office. It is not necessary to run a routing protocol to advertise just one network, especially when we have a default route on the branch office router. Define a static route on the central site router that provides a route for the branch office Ethernet network.

    What is the command to add a static route that defines a route for the branch office Ethernet?

    Add the command to the central site router.

  5. Rather than adding a static route to each router at the central site, it make more sense to redistribute that route into IGRP and let the routing protocol carry it to the rest of the central site.

    What commands are used to redistribute the static route into IGRP?

    Add the commands to the central site router.

  6. For troubleshooting purposes, we want to make sure that we have routes in the core network for the ISDN BRI link. This is so network engineers at the central site can ping the remote side of the ISDN BRI link to verify its operation. The easiest way to do this is to add the BRI network to our list networks running IGRP.

    However, by adding the BRI network to IGRP, we will be forcing route updates to be sent out on that network. Since that will consume valuable bandwidth on this low speed link, we will disable IGRP routing updates to exit the BRI interface using the passive-interface command. This will still allow us to accomplish our goal of adding the BRI network to IGRP without wasting bandwidth with route updates.

    On the central site router:

    CentralRouter(config)#router igrp 100
    CentralRouter(config-router)#passive-interface bri0/0

  7. On your core router, check the IP route table for a route to the branch office Ethernet. Do you see a route for it? 


  8. Try to ping the branch office Ethernet (192.168.1.1) from the core router. Watch the BRI interfaces on the central and branch office routers by using the show interface and LEDs on the front of the router. Can you ping it?

    If you couldn't ping 192.168.1.1 but you did see the BRI interface come up, what would you check first?

  9. Make sure on the central site router that we are not sending out IGRP routing updates on the BRI interface. What command would we use to do that?