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352-001 · Question #675

Which two options are characteristics of DMVPN as related to IP multicast? (Choose two.)

The correct answer is A. The RP should be placed either in the core network or on the DMVPN headend. C. The source of the multicast stream is typically placed at the core.. In DMVPN, the RP should reside at the headend or core network, and multicast sources are typically placed at the core to ensure efficient hub-based replication to all spokes.

Designing Network Services

Question

Which two options are characteristics of DMVPN as related to IP multicast? (Choose two.)

Options

  • AThe RP should be placed either in the core network or on the DMVPN headend.
  • BThe RP is typically placed at the spoke router.
  • CThe source of the multicast stream is typically placed at the core.
  • DWhenthe multicast source is at a spoke, the data flows directly towards the spokes that want to
  • EMulticast on DMVPN is similar in behavior to the broadcast multi-access network.

How the community answered

(45 responses)
  • A
    73% (33)
  • B
    7% (3)
  • D
    4% (2)
  • E
    16% (7)

Why each option

In DMVPN, the RP should reside at the headend or core network, and multicast sources are typically placed at the core to ensure efficient hub-based replication to all spokes.

AThe RP should be placed either in the core network or on the DMVPN headend.Correct

Placing the RP at the DMVPN headend or in the core network ensures all spokes can register and join multicast groups efficiently, since the hub has full connectivity to every spoke via mGRE tunnels. This avoids the inefficiency of multicast traffic having to traverse the hub twice when the RP is located at a spoke.

BThe RP is typically placed at the spoke router.

Placing the RP at a spoke is inefficient because all multicast registrations and join messages must still travel through the hub, adding latency and unnecessary processing load on the hub router.

CThe source of the multicast stream is typically placed at the core.Correct

When the multicast source resides in the core, traffic is injected at the hub and replicated directly to all interested spokes without requiring spoke-to-spoke tunnels, simplifying the multicast distribution tree and reducing hub load.

DWhenthe multicast source is at a spoke, the data flows directly towards the spokes that want to

When a multicast source is at a spoke in DMVPN, traffic flows to the hub first and is then replicated to interested spokes; direct spoke-to-spoke multicast without hub involvement is not the default DMVPN multicast behavior.

EMulticast on DMVPN is similar in behavior to the broadcast multi-access network.

DMVPN operates over an NBMA (Non-Broadcast Multi-Access) topology, not a broadcast multi-access network, so multicast requires explicit configuration via mGRE tunnels and NHRP rather than native broadcast replication.

Concept tested: DMVPN IP multicast RP placement and traffic flow

Source: https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/dmvpn/DMVPN_Nhrp_Multicast.html

Topics

#DMVPN#IP multicast#RP placement#multicast source

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