If a network received a multicast packet, based on the source address of the packet, it was found that the route existed in the unicast routing table, MBGP routing table and multicast static routing…

Question

Options

• A1: Multicast static routing; 2: MBGP routing; 3: Unicast routing
• B
• C
• D

• A
  84% (51)
• B
  10% (6)
• C
  5% (3)
• D
  2% (1)

Explanation

Option A is correct because when RPF (Reverse Path Forwarding) lookup finds matching entries across multiple routing tables with identical priority values and prefix lengths, the router applies a fixed table-type precedence: multicast static routes always win first, followed by MBGP routes, with unicast routes as the last resort. This hierarchy exists because multicast static routes represent explicit administrative intent and are most specific to multicast forwarding; MBGP carries multicast-specific topology built for PIM RPF lookups, making it more reliable than generic unicast paths; unicast routing is a fallback that knows nothing about multicast topology and may yield suboptimal RPF results.

The distractors fail because any ordering that places unicast above MBGP, or MBGP above multicast static, contradicts this fixed precedence - the table type acts as a tiebreaker after preference value and mask length are already equal, and the standard (used in Huawei and similar vendors) consistently ranks dedicated multicast sources over general-purpose ones.

Memory tip: Think "most dedicated wins" - Static Multicast is written just for this packet, MBGP was built for multicast, and Unicast merely happens to know the source. The more multicast-specific the table, the higher its RPF priority.

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