300-510 SPRI: Implementing Cisco Service Provider Advanced Routing SolutionsDemo

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QuestionQ169

Multicast Routing

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Refer to the exhibit. R21 is a multicast source that sends multicast traffic for 224.1.1.1 to R23, with RP22 acting as the rendezvous point inside AS65222. A network engineer observes that when R21 fails, R12 in AS65111 begins sending the same multicast group, 224.1.1.1, through RP11. Which action resolves the issue?

  • A Advertise RP2 with a high focal preference in AS65222.
  • B Enable passive interface under EIGRP between the two autonomous systems.
  • C Disable PIM sparse mode between RP11 and RP22 in the two autonomous systems.
  • D Block service groups 224.0.1.39 and 224.0.1.40 between the two autonomous systems.
Explanation

Auto-RP distributes RP-to-group mappings with RP-Announce messages on 224.0.1.39 and RP-Discovery messages on 224.0.1.40. These messages must not leak across the autonomous-system boundary, because doing so lets one AS learn and act on the other AS's RP mappings. Blocking both Auto-RP service groups at the boundary keeps the RP domains separate and prevents the incorrect forwarding behavior.

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