Lab 8.7.5 BGP Route Aggregation

Objectives:

  • Configure CIDR with BGP.

Scenario:

Router B is receiving advertisements about network 172.50.0.0 and 172.60.0.0 from Router C in AS 100. Router B needs to only advertise the 172.0.0.0 prefix to the Internet and other Autonomous Systems.

Tasks:

  1. Cable and configure the lab as shown in the diagram. Use BGP as your routing protocol. On Router-C, advertise both networks 172.50.0.0 and 172.60.0.0 with the network command. Don't forget to advertise network 192.168.10.0 on Router A also. Before moving on to the next step, be sure that Router-A and Router-C are seeing each others routes with the show ip route and show ip bgp commands.




  2. Look at the routing table of Router A, what routes do you see?




  3. Login to Router-B. To enable the aggregation of the 172.0.0.0 networks, issue the following command:

    Router-B(config-router)#aggregate-address 172.0.0.0 255.0.0.0
    Router-B#
    clear ip bgp *

  4. Now look at the routing table of Router-A. What routes do you see that begin with the prefix 172.x.x.x?


  5. Did you see more than you planned? ________ Suppose we only want the 172.0.0.0 prefix to be advertised and not any more specific routes. Issue the following command to make this happen:

Router-B(config-router)#aggregate-address 172.0.0.0 255.0.0.0 summary-only
Router-B#clear ip bgp *

  1. Go back to Router-A and examine the routing table. What routes do you see that begin with the prefix 172.x.x.x?