What are three issues that may cause the forming a BGP neighbor relationship to fail? (Choose three.)
- TCP port 169 being blocked by a firewall
- broken Layer 3 connectivity
- the path to the neighbor being through the default route
- interface being down
- only iBGP being configured on the router
- the holddown timer not matching between BGP peers
Explanation: Some of the reasons that a BGP neighbor relationship might not form are as follows:
- Interface is down : The interface must be up/up.
- Layer 3 connectivity is broken : The IP address for a neighbor must be reachable.
- Path to the neighbor is through the default route : A neighbor must be reachable using a route other than the default route.
- ACLs : An access control list (ACL) or a firewall may be blocking TCP port 179.
- Timers : Timers do not have to match; however, if the minimum holddown from neighbor option is set, it could prevent a neighbor adjacency.
More Questions: CCNP Enterprise: Advanced Routing (Version 8.0) – BGP Exam