Refer to the exhibit. Which statement about this command is true?

Question

Options

• AIt must be configured on each PE router to enable the PE routers to receive multicast traffic for
• BIt is used to set the designated router on a link using PIM-SM.
• CIt must be configured on the PE and CE router to enable MP-BGP to send labels for CSC.
• DIt is used to set the router that will server as the root bridge for STP.

• A
  81% (47)
• B
  10% (6)
• C
  3% (2)
• D
  5% (3)

Explanation

Option A is correct because the command shown - likely an ip pim or multicast-routing related command - must be applied individually on each PE router in an MPLS VPN topology to enable those routers to participate in multicast distribution trees and receive multicast traffic for the VPN. Multicast VPN (MVPN) requires each PE to be explicitly configured; it does not propagate automatically across the MPLS backbone.

Why the distractors are wrong:

• B is wrong because the Designated Router (DR) in PIM-SM is elected automatically via the PIM hello process, not set by a static command like this.
• C is wrong because MP-BGP label distribution for Carrier Supporting Carrier (CSC) involves BGP label unicast configuration (send-label), not a multicast-specific command.
• D is wrong because STP root bridge selection is a Layer 2 concept controlled via spanning-tree priority, completely unrelated to MPLS/multicast PE configuration.

Memory tip: Think "PE = Per router, Every router" - in MPLS multicast VPNs, there's no shortcut; each PE must be individually configured because the multicast control plane doesn't auto-discover peers the way BGP session advertisements do. If you see a question about multicast + PE routers + "must be configured on each," option A pattern is almost always your answer.

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