A network administrator notices that the BGP state drops and logs are generated for missing BGP hello keepalives. What is the potential problem?

ccnp-dump
ccnp-route-dump
ccnp-route

#1

A network administrator notices that the BGP state drops and logs are generated for missing BGP hello
keepalives. What is the potential problem?
A. Incorrect neighbor options
B. Hello timer mismatch
C. BGP path MTU enabled
D. MTU mismatch

Correct Answer: D

Explanation:
BGP neighbors form; however, at the time of prefix exchange, the BGP state drops and the logs generate
missing BGP hello keepalives or the other peer terminates the session.
Here are some possible causes:

  • The interface MTU on both routers do not match.
  • The interface MTU on both routers match, but the Layer 2 domain over which the BGP session is formed does not match.
  • Path MTU discovery determined the incorrect max datasize for the TCP BGP session. *The BGP Path
    Maximum Transmission Unit Discovery (PMTUD) could be failing due to PMTUD ICMP packets blocked
    (firewal or ACL)