I have a router in Location A1 (Router-A1) and A2 (Router-A2) which is establishing EIGRP neighborship with location B (Router-B). Location B router establishes eBGP neighborship with Location C (Router-C). A subnet from A1 and A2 is getting advertised via EIGRP to location B. From location A1 the subnet is getting advertised as /26 and from location A2, the subnet is getting advertised as /32. Advertisement from A1 was found to be received with a better metric and hence it was installed in EIGRP routing table of B.
Router B advertises the same subnet to eBGP peer using network statement and an outbound prefix list is also configured towards this eBGP peer. Both the network statement and the prefix-list is found to have the advertisement as /26.
Router-A1 is being shutdown for some reason and now Router B doesn't receive the routing information for this subnet. Although Router-B still receives a /32 route for an IP address within this subnet. But the issue reported is that the eBGP at location C i.e., Router-C is not able to see this network (/26 or /32) in their BGP routing table.
Issue was fixed by adding a /32 network statement and /32 prefix-list in the BGP process of Router-B.
Is this issue relevant to BGP synchronization rule. Even though a /32 route is visible in Router-B, and the whole of /26 is advertised in the BGP network statement and prefix-list, the eBGP peer doesn't seem to receive it on its routing table. Router-B's BGP advertised routes also doesn't have this /32 advertised outside.
