The auto-RP protocol consists of announcing, mapping, and discovery functions. The Internet Assigned Numbers Authority (IANA) has assigned two group addresses, 224.0.1.39 and 224.0.1.40, for auto-RP.
Three roles can be configured in auto-RP:
candidate RP (CRP)
The candidate RP is a router that aims to be an RP for a multicast group using RP-announce messages.
mapping agent
The mapping agent sees the RP-announce messages and selects the best RP based on the highest IP address for the advertised multicast group. Then, it floods the network with RP-mapping messages about which RPs to use for that group.
auto-RP listener
The auto-RP listener forwards traffic about the multicast group throughout the network so that the routers that are not directly attached to the mapping agent or to the RP can also learn the RP address. When the listener functionality is enabled, the router uses dense mode only for the two dedicated multicast group addresses.
SR OS supports all auto-RP functionality under GRT and MVPN (NG-MVPN and Rosen MVPN with BGP SAFI).