InBidirectional PIM, redundancy for Rendezvous Points (RPs) is provided through thePhantom RPmechanism. This setup offers HA by:
A. Using two phantom RP addresses: You configure two RPs with the same virtual RP address but advertise them with loopback interfaces having different subnet masks. These phantom RPs allow seamless failover between active and standby RPsdatatracker.ietf.org+14arubanetworking.hpe.com+14examtopics.com+14ciscolive.com+3examtopics.com+3ccie-sp.gitbook.io+3learnwithsalman.com+4lostintransit.se+4learningnetwork.cisco.com+4.
F. Controlling routing through a longest match prefix: The active RP is chosen based on unicast routing — the loopback with the longest prefix match to the RP address is preferred. If that RP fails, the IGP converges and the standby with the next-longest prefix becomes activearubanetworking.hpe.com.
This combined mechanism aligns with CCDE v3.1 design principles by ensuring multicast HA with minimal complexity — no MSDP involvement and leveraging existing IGP behaviors.
Why other options are incorrect:
B&D: Changing administrative distance or protocol advertisement doesn't inherently establish redundancy in Bidir-PIM RP selection.
C: Static mroutes are static and don’t support dynamic redundancy or failover.
E: Anycast RP with MSDP is not supported or needed in Bidir-PIM environments.
This design ensures robust, seamless RP redundancy using phantom RPs with longest-prefix selection logic, remaining cost-effective and operationally concise.
https://community.cisco.com/t5/networking-knowledge-base/rp-redundancy-with-pim-bidir-phantom-rp/ta-p/3117191
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