What are three issues that may cause the forming a BGP neighbor relationship to fail? (Choose three.)

Question:

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.

Exam with this question: CCNP Enterprise: Advanced Routing (Version 8.0) – BGP Exam