In some situations you can see following error message while trying to establish BGP neighborship

%BGP_SESSION-5-ADJCHANGE: neighbor 192.168.0.2 IPv4 Unicast topology base removed from session  Unknown path error

This can be misconfiguration or internal bug described (or rather just mentioned because I’d say bug description is almost empty) in CSCsy10339 bug ticket if you are using release prior to 12.2(33)XNE. If this is misconfiguration you’d rather expect error message like

%BGP_SESSION-5-ADJCHANGE: neighbor 192.168.0.2 IPv4 Unicast topology base removed from session  Peer closed the session

. This can be quite confusing and leads to looking for problem elsewhere than it exists.