Multicast mapping agent IGMP membership report

In a Multicast topology, when using a mapping agent with Multicast PIM sparse mode and Auto-RP, the 224.0.1.39 multicast address is used by mapping agents to listen for candidate announcements. It is therefore expected that this group appear in the multicast routing table of the mapping agent.

However, it may also appear on non-mapping-agent routers as well. This is because whenever the send-rp-discovery command is applied to a multicast router, it sends out an IGMP membership report for this group. This means that directly connected neighbors of the mapping agent will also have this group in the multicast routing table.

Links:

https://forum.networklessons.com/t/multicast-pim-auto-rp/1339/52?u=lagapides

https://networklessons.com/cisco/ccie-routing-switching/multicast-ip-pim-auto-rp

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