For which reason can two BGP peers fail to establish a neighbor relationship?

Question

Options

• ATheir BGP send-community strings are misconfigured
• BTheir BGP timers are mismatched
• CTheir remote-as numbers are misconfigured
• DThey are both activated under an IPv4 address family

• A
  2% (1)
• C
  93% (42)
• D
  4% (2)

Explanation

BGP neighbor relationships require strict matching of the remote-as number configured on each peer. When Router A configures 'neighbor X.X.X.X remote-as 65001', it expects the peer to belong to AS 65001. If the peer actually belongs to a different AS, the OPEN message exchange fails and the session is rejected. Option A is incorrect because send-community is an outbound policy that affects attribute propagation after the session is established, not session formation. Option B is incorrect because BGP timers (hold-time, keepalive) are negotiated during the OPEN phase-BGP uses the lower of the two peers' values, so a mismatch doesn't prevent the session from forming. Option D is incorrect because activating both peers under an IPv4 address family is required for exchanging IPv4 prefixes and would not cause a failure.

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