Cisco CCNP and CCIE Study Notes

Consider two routers connected back-to-back with each other via a pair of serial interfaces. The routers are running RIP to advertise their loopbacks to each other. Here is the config from the two routers

Router1

interface Loopback0
 ip address 1.1.1.1 255.255.255.255
!
interface Serial2
 ip address 20.20.20.1 255.255.255.0
 no keepalive
!
interface Serial3
 ip address 30.30.30.1 255.255.255.0
 no keepalive

Router2

interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!
interface Serial2
 ip address 20.20.20.2 255.255.255.0
 no keepalive
!
interface Serial3
 ip address 30.30.30.2 255.255.255.0
 no keepalive

Now consider the following output from "show ip route 2.2.2.2" on router R1

R1#show ip route 2.2.2.2
Routing entry for 2.0.0.0/8
  Known via "rip", distance 120, metric 1
  Redistributing via rip
  Last update from 20.20.20.2 on Serial2, 00:00:10 ago
  Routing Descriptor Blocks:
  * 20.20.20.2, from 20.20.20.2, 00:00:10 ago, via Serial2
      Route metric is 1, traffic share count is 1

Note that R1 sees only one route to 2.2.2.2 via 20.20.20.2 even though clearly it has another path with the same cost via 30.30.30.2.

Your task is to determine using the information provided what must have been configured under the rip router configuration to cause only one path to 2.2.2.2 to be installed in the routing table.