Anycast RP through MSDP
PIM-SM requires only one active RP to serve each multicast group. If the active RP fails, the multicast traffic might be interrupted. The Anycast RP mechanism enables redundancy backup between two or more RPs by configuring multiple RPs with the same IP address for one multicast group. A multicast source registers with the closest RP or a receiver joins the closest RP to implement source information synchronization.
For Anycast RP implemented through MSDP, all member RPs in the Anycast RP set have the same IP address, and MSDP peering connections are established between the RPs.
As shown in Figure 63, within a PIM-SM domain, a multicast source sends multicast data to multicast group G, and the receiver joins the multicast group. To implement Anycast RP through MSDP, complete the following tasks:
Assign the same IP address (known as Anycast RP address, typically a private address) to an interface on Device A and Device B.
Configure the interfaces as C-RPs.
Establish an MSDP peering relationship between Device A and Device B.
Figure 63: Anycast RP through MSDP
The following describes how Anycast RP through MSDP is implemented:
After receiving the multicast data from Source, the source-side DR registers with the closest RP (RP 1 in this example).
After receiving the IGMP report message from the receiver, the receiver-side DR sends a join message toward the closest RP (RP 2 in this example). An RPT rooted at this RP is established.
The RPs share the registered multicast source information through SA messages. After obtaining the multicast source information, RP 2 sends an (S, G) source-specific join message toward the source to create an SPT.
When the multicast data reaches RP 2 along the SPT, the RP forwards the data along the RPT to the receiver. After receiving the multicast data, the receiver-side DR determines whether to initiate an RPT-to-SPT switchover process based on its configuration.