Hello Gowthamraj
In order to explain it more clearly, take a look at the following diagram of a network using confederations:
Note the following:
- If R5 has a prefix with a no-advertise community, it will not be sent to any BGP neighbor.
- If R5 has a prefix with no-export community, it will be sent to all neighbors within AS2, specifically, R3, R2, and R4.
- If R5 has a prefix with local-as community, it will be sent only within subAS 35, specifically, only to R3.
- If R5 has a prefix with internet community (which is the default if no communities are configured) then it will be sent to all routers in all AS’es including R1.
I hope this has been helpful!
Laz