What is the result of a successful RPF check?

Question

Options

• APacket is dropped because it arrived on the interface that used to forward the packet back to
• BPacket is dropped because it arrived on the interface that used to forward the packet back to
• CPacket is forwarded because it arrived on the interface that used to forward the packet back to
• DPacket is forwarded because it arrived on the interface that used to forward the packet back to

• B
  4% (1)
• C
  4% (1)
• D
  92% (23)

Explanation

Routers perform a reverse path forwarding (RPF) check to ensure that arriving multicast packets were received through the interface that is on the most direct path to the source that sent the packets. An RPF check is always performed regarding the incoming interface, which is considered to be the RPF interface. The RPF check will succeed if the incoming interface is the shortest path to the source. The router determines the RPF interface by the underlying unicast routing protocol or the dedicated multicast routing protocol in cases where one exists. An example of a dedicated multicast routing protocol is MP-BGP. It is important to note that the multicast routing protocol relies on the underlying unicast routing table. Any change in the unicast routing table immediately triggers an RPF recheck on most modern routers.

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