RIPv2 Authentication one sided

When RIP v2 authentication is enabled on 1 router it means it'll authenticate the updates coming from peer and not the updates being sent to peer.

Example here enabling authentication only on R2

R2#sh run int s0/0
Building configuration...

Current configuration : 193 bytes
!
interface Serial0/0
 ip address 192.168.12.2 255.255.255.0
 ip rip authentication mode md5
 ip rip authentication key-chain cisco


Results of debug

*Mar  1 00:10:26.535: RIP: ignored v2 packet from 192.168.12.1 (invalid authentication)

But if we check routing table on R1 and R2

R1#sh ip route 2.2.2.2
Routing entry for 2.2.2.2/32
  Known via "rip", distance 120, metric 1
  Redistributing via rip
  Last update from 192.168.12.2 on Serial0/0, 00:00:01 ago
  Routing Descriptor Blocks:
  * 192.168.12.2, from 192.168.12.2, 00:00:01 ago, via Serial0/0
      Route metric is 1, traffic share count is 1



Router 1 still learns about routes from R2


But router 2 doesn't learn any routes from R1



R2#sh ip route 1.1.1.1
Routing entry for 1.1.1.1/32
  Known via "rip", distance 120, metric 3
  Redistributing via rip
  Last update from 192.168.24.4 on Serial0/1, 00:00:21 ago
  Routing Descriptor Blocks:
  * 192.168.24.4, from 192.168.24.4, 00:00:21 ago, via Serial0/1    <<<<<<< From R4
      Route metric is 3, traffic share count is 1