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{ Anycast RP address—IP address of the Anycast RP set for communication within the PIM-SM
domain. It is also known as RPA.
As shown in Figure 33, RP
1, RP 2, and RP 3 are members of an Anycast RP set.
Figure 33 Anycast RP through PIM-SM
The following describes how Anycast RP through PIM-SM is implemented:
a. RP 1 receives a register message destined to the Anycast RP address (RPA). Because the
message is not from other Anycast RP members (RP 2 or RP 3), RP 1 assumes that the register
message is from the DR. RP 1 changes the source IP address of the register message to its own
address and sends the message to the other members (RP 2 and RP 3).
If a router acts as both a DR and an RP, it creates a register message, and then forwards the
message to the other RP members.
b. After receiving the register message, RP 2 and RP 3 find out that the source address of the
register message is an Anycast RP member address. They stop forwarding the message to
other routers.
In Anycast RP implementation, an RP must forward the register message from the DR to other
Anycast RP members to synchronize multicast source information.
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