3Com Switch 8800 Advanced Software V5 Configuration Guide

614 CHAPTER 43: MSDP CONFIGURATION

An EBGP route exists between two MSDP peers in different ASs. Because the SA

message is from an MSDP peer (RP 7) in a different AS, and the MSDP peer is the

next hop on the EBGP route to the source-side RP, RP 8 accepts the message and

forwards it to its other peer (RP 9).

7 When RP 9 receives the SA message from RP 8

Because RP 9 has only one MSDP peer, RP 9 accepts the SA message.

SA messages from other paths than described above will not be accepted nor

forwarded by MSDP peers.

Implementing intra-domain Anycast RP by leveraging MSDP peers

Anycast RP refers to such an application that enables load balancing and

redundancy backup between two or more RPs within a PIM-SM domain by

configuring the same IP address for, and establishing MSDP peering relationships

between, these RPs.

As shown in Figure 189, within the same PIM-SM domain, a multicast source

sends multicast data to multicast group G, and Receiver is a member of the

multicast group. To implement Anycast RP, configure the same IP address (known

as anycast RP address, typically a private address) on Router A and Router B,

configure these interfaces as C-RPs, and establish an MSDP peering relationship

between Router A and Router B.

Usually an Anycast RP address is configured on a logic interface, like a loopback

interface.

Figure 189 Typical network diagram of Anycast RP

The work process of Anycast RP is as follows:

1 The multicast source registers with the nearest RP. In this example, Source registers

with RP 1, with its multicast data encapsulated in the register message. When the

2 Receivers send join messages to the nearest RP to join in the RPT rooted as this RP.

In this example, Receiver joins the RPT rooted at RP 2.

3 RPs share the registered multicast information by means of SA messages. In this

example, RP 1 creates an SA message and sends it to RP 2, with the multicast data

SA message

Source Receiver

Router A

Router B

RP 1 RP 2

PIM-SM

MSDP peers