The main function of MBGP is to help perform RPF verification of cross-domain multicast flows.

Question

Options

• ATRUE
• BFALSE
• C
• D

• A
  83% (20)
• B
  4% (1)
• C
  8% (2)
• D
  4% (1)

Explanation

MBGP (Multicast BGP) is an extension of BGP that advertises multicast-capable routes separately from unicast routes, giving multicast routers a dedicated routing table to consult during RPF (Reverse Path Forwarding) checks. RPF verification works by confirming that a multicast packet arrives on the interface that leads back toward the source - and for cross-domain flows, unicast BGP routes alone may point toward a different path than the actual multicast topology requires. MBGP solves this by providing accurate multicast-specific reachability information, allowing routers to correctly identify the RPF interface even when unicast and multicast topologies diverge across autonomous systems.

Why B (FALSE) is wrong: The statement is factually accurate - MBGP's primary purpose is precisely to support RPF lookups for inter-domain multicast, so denying it contradicts the protocol's core design goal.

Memory tip: Think of MBGP as giving multicast its own "address book" separate from unicast BGP - without it, cross-domain multicast routers would use the wrong map for the RPF check, causing multicast traffic to be silently dropped.

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