Netgear XCM8806 - 8800 SERIES 6-SLOT CHASSIS SWITCH ユーザーズマニュアル

Anycast RP

Anycast RP is an application of MSDP that allows multiple RPs to operate simultaneously in 
a PIM-SM domain. Without anycast RP, multiple routers can be configured as candidate RPs, 
but at any point in time, only one router can serve as RP. Because anycast RP allows 
multiple RPs to be simultaneously active, anycast RP provides both load sharing and 
redundancy, as each RP serves the receivers that are closest to it in the network and can 
take over for additional receivers if another RP fails.

In an anycast RP topology, all RPs in a PIM-SM domain are configured with the same IP 
address on a loopback VLAN. The loopback VLAN IP address should have a 32-bit mask, so 
that it specifies a host address. All the routers within the PIM-SM domain select the nearest 
RP for each source and receiver. If the senders and receivers within the PIM-SM domain are 
distributed evenly, the number of senders that register with each RP is approximately equal.

Another requirement of the anycast RP topology is that MSDP must run on all RPs in the 
PIM-SM domain, so all RPs are also MSDP peers. NETGEAR recommends that you 
configure an MSDP mesh connection between all MSDP peers in the domain.

Whenever any multicast source becomes active, this information is sent in an MSDP SA 
message to the other MSDP peers in the domain, announcing the presence of the source. If 
any RP within the domain fails, the IP routing protocol mechanism ensures that next 
available RP is chosen. If a sender registers with one RP and a receiver joins another RP, the 
information shared through MSDP enables PIM-SM to establish an SPT between the 
receiver and the source.

NETGEAR recommends that you configure anycast RP peers in a 

mesh topology.

The exchange of information in an anycast RP process works as follows:

When the first-hop router sends a PIM Register message to the nearest RP, the PIM 

router checks to see if the nearest RP is the RP for the group.

If the nearest RP is the RP for the group, an MSDP SA message is created and 

forwarded to the other MSDP peers. 

The MSDP SA message includes the configured originator ID, which is a mandatory 

configuration component.

Each remote peer checks the RPF of the originator ID address and informs the PIM 

process on that remote router about active multicast sources.

Remote receivers get data packets through the remote shared tree, and can then switch 

over to the SPT by sending join messages directly towards the source.

To configure anycast RP, do the following at each anycast RP router:

Create and configure a loopback VLAN using the following commands:

create vlan <vlan_name> {vr <vr-name>}