Which relationship between IBGP and the underlying physical topology is true?

Question

Options

• AiBGP full mesh requirement does not dictate any specific network topology.
• BiBGP can worn only on a ring network topology with a link-state protocol like OSPF or IS-IS
• CiBGP full mesh requires an underlying fully meshed network topology.
• DiBGP does not work on a ring network topology even with an underlying IGP.

• A
  95% (18)
• C
  5% (1)

Explanation

iBGP requires a logical full mesh among all iBGP speakers inside an AS because iBGP does not re-advertise routes learned from one iBGP peer to another iBGP peer (split-horizon rule). However, this logical full mesh is completely independent of the underlying physical topology. iBGP sessions are carried over TCP, and TCP reachability between any two iBGP speakers can be provided by any IGP (OSPF, IS-IS, EIGRP, etc.) running over whatever physical topology exists - ring, hub-and-spoke, partial mesh, or full mesh. Option B is false; iBGP is not restricted to ring topologies. Option C is false; a logical iBGP full mesh does not require a physically fully meshed network. Option D is false; iBGP functions fine on ring topologies when an IGP provides underlying reachability. Route Reflectors and Confederations can also eliminate the logical full-mesh requirement entirely.

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