Router B is receiving advertisements
about network 172.50.0.0 and 172.60.0.0 from Router C in AS 100.
Router B should only be able to advertise 172.0.0.0/8 to AS 300
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. You will also need to advertise the aggregate-address
172.0.0.0 255.0.0.0 on Router-C. 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?
To permit only 172.0.0.0/8 updates,
we are going to configure a prefix list called supernetonly. To do
this, issue the following command:
Router-B(config)# ip prefix-list
supernetonly permit 172.0.0.0/8
Just like an access-list, this has
no effect until we assign it to a neighbor. To assign the prefix
list to Router-A, issue the following command:
Router-B(config-router)#neighbor
10.10.2.2 prefix-list supernetonly out
Clear your BGP routing table on
Router-A with the clear ip bgp * command and examine the routing
table of Router-A. What routes do you see now?