I am advertising a loopback from a router and the mask on the loopback is same as the interface sending out the RIP updates.
int loopback 0
ip add 192.168.254.1 255.0.0.0
int serial 1/0
ip address 220.127.116.11 255.0.0.0 (this interface sending/receiving RIP updates)
The problem is the other RIP router is not receiving the RIP update for 192.168.254.0 subnet when the mask is the same as the serial. my understanding is if the update for 192.168.254.0 is not the same major network as the interafce advertising the update, then it advertise the update despite the mask being the same??? since ripv1 is a classful, it should advertise 192.168.254.0 as /24?
this is what i'm seeing on r1
r1#sh ip rip database
 via 0.0.0.0,