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352-001 · Question #675
352-001 Question #675: Real Exam Question with Answer & Explanation
The correct answer is A: The RP should be placed either in the core network or on the DMVPN headend.. 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.
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.
Explanation
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.
Common mistakes.
- B. 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.
- D. 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.
- E. 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
Reference. https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/dmvpn/DMVPN_Nhrp_Multicast.html
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