CX11x, CX31x, CX710 (Earlier Than V6.03), and CX91x Series Switch Modules V100R001C10 Configuration Guide 12

When the multicast source and the receiver are located in different PIM-SM domains of the same AS, you can configure MSDP peers on the RPs to implement inter-domain multicast.

Figure 8-77 PIM-SM inter-domain multicast in an AS

As shown in Figure 8-77, the MSDP peer relationship is set up between RPs of two PIM-SM domains. In this manner, information about the multicast source is shared between the two domains.

Both Multiprotocol Border Gateway Protocol (MBGP) connections and MSDP connections are TCP connections. You can set up an MBGP peer relationship between two MSDP peers to ensure that SA messages can pass the RPF check.

Figure 8-78 Inter-AS multicast using MBGP and MSDP

As shown in Figure 8-78, the RPs in different PIM-SM domains are not directly connected to each other and the RPs and ASBRs are deployed on different routers. After you set up MSDP peer relationships between the RPs, you can also set up MBGP peer relationships between them to ensure that SA messages can pass the RPF check.

• IBGP: set up IBGP peer relationships for RPs in the same AS, such as RP1 and RP2, and RP3 and RP4.

• EBGP: set up EBGP peer relationships for RPs in different ASs, such as RP1 and RP3, and RP2 and RP4.

The MBGP peer relationship and MSDP peer relationship must be set up on the same interface. MBGP and MSDP are frequently used together. For details about MBGP, see "BGP" in the CX11x&CX31x&CX91x Series Switch Modules Configuration Guide- IP Routing.

As mentioned in RPF Rules of SA Messages, if an SA message is sent by an RPF peer, the message is accepted and forwarded to other MSDP peers. If you manually specify MSDP peers as static RPF peers to one another, these RPF peers accept SA messages without performing the RPF check.

Incorrect static RPF configurations may lead to loops of SA messages. Exercise caution when you configure static RPF peers. Static RPF peer relationships are usually set up among MSDP peers in multiple ASs.

Figure 8-79 Inter-AS multicast using static RPF peers

MSDP peer relationships are set up between RPs to exchange SA messages, so that source information registered locally can be shared by the RPs. Anycast RP is the application of this feature in one PIM-SM domain.

In a traditional PIM-SM domain, all multicast groups map to one RP. When the network is overloaded or the traffic volume is high, many network problems occur, such as the heavy pressure of the RP, the slow convergence after the RP fails, and the non-optimal multicast forwarding path. By using Anycast RP, you can configure multiple RPs in a PIM-SM domain, assign the same IP address to these RPs, and set up MSDP peer relationships between these RPs. In this manner, the optimal RP path and load balancing can be implemented.

As shown in Figure 8-80, in the PIM-SM domain, the multicast sources, Source1 and Source2, send multicast data to the multicast group G. Receiver1 and Receiver2 are members of group G.

Figure 8-80 Networking diagram of Anycast RP

Do as follows to apply Anycast RP in a PIM-SM domain:

1. Select several routers in the PIM-SM domain, such as RouterA and RouterB in Figure 8-80.
2. Choose one loopback interface from each router, such as Loopback1 in Figure 8-80, and assign the same address to these interfaces.
3. Configure the RP. You can configure static RPs or C-RPs, as shown in Figure 8-80.
   • Static RP: Configure static RPs on all PIM-SM routers, and use the address of the interface Loopback1 on RouterA as the address of the RPs.
   • C-RP: Configure the two Loopback1 interfaces on RouterA and RouterB as C-RPs. Configure a C-BSR on the network. Ensure that the address of the C-RP must be different from the address of the C-BSR.
4. Set up an MSDP peer relationship between RouterA and RouterB. Do not use the interface addresses of the RPs.