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:
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.
Look at the routing table of Router A, what routes do you see?
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 *
Now look at the routing table of Router-A. What routes do you
see that begin with the prefix 172.x.x.x?
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 *
Go back to Router-A and examine the routing table. What routes
do you see that begin with the prefix 172.x.x.x?