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352-001 · Question #25

Which statement is true about connecting an IP multicast domain that is operating in PIM dense mode to a PIM sparse mode domain?

The correct answer is A. The interconnection must be made at the rendezvous point of the PIM sparse mode domain.. To interconnect a PIM dense mode domain with a PIM sparse mode domain, the border connection must be made at the Rendezvous Point of the sparse mode domain so sources can register and receivers can join the shared tree.

Designing Network Services

Question

Which statement is true about connecting an IP multicast domain that is operating in PIM dense mode to a PIM sparse mode domain?

Options

  • AThe interconnection must be made at the rendezvous point of the PIM sparse mode domain.
  • BThe connection can be made at any location in the network, as PIM sparse mode will inter-operate
  • CPIM dense mode and sparse mode domains are not inter-operable and cannot be connected.
  • DThe connection can be made at any location in the network, but PIM sparse mode and PIM dense

How the community answered

(34 responses)
  • A
    71% (24)
  • B
    9% (3)
  • C
    18% (6)
  • D
    3% (1)

Why each option

To interconnect a PIM dense mode domain with a PIM sparse mode domain, the border connection must be made at the Rendezvous Point of the sparse mode domain so sources can register and receivers can join the shared tree.

AThe interconnection must be made at the rendezvous point of the PIM sparse mode domain.Correct

PIM sparse mode relies on the RP as the central registration and join point for multicast groups. When a PIM-DM domain is connected to a PIM-SM domain, the border router must attach at the RP so that sources in the dense mode domain can register with the RP via PIM Register messages, allowing sparse mode receivers to join the shared distribution tree and receive traffic.

BThe connection can be made at any location in the network, as PIM sparse mode will inter-operate

PIM-DM (flood-and-prune) and PIM-SM (explicit join via RP) use fundamentally different forwarding mechanisms that require RP coordination at the boundary, so they cannot interoperate at an arbitrary location.

CPIM dense mode and sparse mode domains are not inter-operable and cannot be connected.

PIM-DM and PIM-SM domains can be interconnected - the requirement is simply that the interconnection point must be at the RP of the sparse mode domain.

DThe connection can be made at any location in the network, but PIM sparse mode and PIM dense

Connecting at any location is insufficient because PIM-SM requires all sources to register at the RP before receivers can build the shared tree and pull traffic.

Concept tested: PIM dense mode to sparse mode domain interconnection

Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti_pim/configuration/xe-16/imc-pim-xe-16-book/imc-sparse-dense.html

Topics

#PIM dense mode#PIM sparse mode#rendezvous point#multicast interoperability

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