Click the exhibit. Assuming that none of the routers within AS 65200 is configured with next-hop-self", what will the BGP update for the 192.168.0.1/27 prefix contain when it arrives at router B?

Question

Options

• AAS Path of 65200 65100, Next Hop of router A.
• BAS Path of 65200 65100, Next Hop of router E.
• CAS Path of 65100, Next Hop of router E.
• DAS Path of 65100, Next Hop of router A.

• A
  4% (1)
• B
  8% (2)
• C
  85% (22)
• D
  4% (1)

Explanation

Option C is correct because when a prefix originates in AS 65100 and is learned by a router in AS 65200 via eBGP, the AS Path at that boundary is simply 65100. When that route is then propagated to Router B via iBGP (internal BGP) within AS 65200, iBGP does not prepend the local AS number to the path - only eBGP advertisements add an AS to the path. Additionally, without next-hop-self configured, iBGP preserves the original Next Hop as learned from the eBGP peer (Router E), rather than replacing it with the advertising router's own address.

• A & B are wrong because they show AS Path "65200 65100" - AS 65200 only prepends itself when advertising the route out to a third external AS, never for iBGP updates within its own AS.
• D is wrong because Router A would only be the Next Hop if next-hop-self were configured, which it explicitly is not in this scenario.

Memory tip: Think "iBGP = Invisible AS, Unchanged Next Hop." iBGP is invisible to the AS Path (adds nothing) and passes the Next Hop through untouched - unless you force a change with next-hop-self.

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