Default Route Generation in RIP

Let us understand default route generation in RIP with help of below topology. The aim is to generate default route on R2 towards R1 and R3 (RIP Domain). R2 is connected to a Service Provider(MPLS VPN or and ISP).  R1 and R3 should be able to ping/reach the Internet IP connected behind R4 (66.66.66.66/32) using the RIP default route.

On R2, In order to generate default route towards LAN network routers R1 and R3, we have to  configure below command in RIP

R2(config)#
R2(config-router)#default-information originate

We can see default route (denoted by R*) on R1 and R3 pointing to R2.

R1#show ip route | i 0.0.0.0/0
R*    0.0.0.0/0 [120/1] via 10.10.12.2, 00:00:19, FastEthernet1/0

R3#show ip route | i 0.0.0.0/0
R*    0.0.0.0/0 [120/1] via 10.10.23.2, 00:00:12, FastEthernet1/0

Let us try to ping an internet IP connected to R4 (66.66.66.66/32) from R1 and R2. Though R1 and R3 do not have route to this Internet IP, but they will be able to reach this using RIP default route.

R1#sh ip route 66.66.66.66
% Network not in table

R3#sh ip  route 66.66.66.66
% Network not in table



R1#ping 66.66.66.66
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 66.66.66.66, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 84/168/220 ms


R3#ping 66.66.66.66
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 66.66.66.66, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 136/159/236 ms


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