Changing an RPF route

As shown in Figure 18:

• PIM-DM runs in the network.

• All switches in the network support multicast.

• Switch A, Switch B and Switch C run OSPF.

• Typically, the receiver host can receive the multicast data from the source through the path: Switch A to Switch B, which is the same as the unicast route.

Configure the switches so that the multicast data from Source travels to the receiver along the following path: Switch A to Switch C to Switch B. This is different than the unicast route.

1. Assign an IP address and subnet mask to each interface according to Figure 18. (Details not shown.)

2. Enable OSPF on the switches in the PIM-DM domain to make sure the following conditions are met: (Details not shown.)

   • The switches are interoperable at the network layer.

   • The switches can dynamically update their routing information.

3. Enable IP multicast routing, and enable IGMP and PIM-DM:

   # On Switch B, enable IP multicast routing.

   <SwitchB> system-view
   [SwitchB] multicast routing
   [SwitchB-mrib] quit
   

   # Enable IGMP on the receiver-side interface (VLAN-interface 100).

   [SwitchB] interface vlan-interface 100
   [SwitchB-Vlan-interface100] igmp enable
   [SwitchB-Vlan-interface100] quit
   

   # Enable PIM-DM on the other interfaces.

   [SwitchB] interface vlan-interface 101
   [SwitchB-Vlan-interface101] pim dm
   [SwitchB-Vlan-interface101] quit
   [SwitchB] interface vlan-interface 102
   [SwitchB-Vlan-interface102] pim dm
   [SwitchB-Vlan-interface102] quit
   

   # On Switch A, enable IP multicast routing, and enable PIM-DM on each interface.

   <SwitchA> system-view
   [SwitchA] multicast routing
   [SwitchA-mrib] quit
   [SwitchA] interface vlan-interface 200
   [SwitchA-Vlan-interface200] pim dm
   [SwitchA-Vlan-interface200] quit
   [SwitchA] interface vlan-interface 102
   [SwitchA-Vlan-interface102] pim dm
   [SwitchA-Vlan-interface102] quit
   [SwitchA] interface vlan-interface 103
   [SwitchA-Vlan-interface103] pim dm
   [SwitchA-Vlan-interface103] quit
   

   # Enable IP multicast routing and PIM-DM on Switch C in the same way Switch A is configured. (Details not shown.)

4. Display the RPF route to Source on Switch B.

   [SwitchB] display multicast rpf-info 50.1.1.100
    RPF information about source 50.1.1.100:
        RPF interface: Vlan-interface102, RPF neighbor: 30.1.1.2
        Referenced route/mask: 50.1.1.0/24
        Referenced route type: igp
        Route selection rule: preference-preferred
        Load splitting rule: disable
   

   The output shows that the current RPF route on Switch B is contributed by a unicast routing protocol and the RPF neighbor is Switch A.

5. Configure a static multicast route on Switch B and specify Switch C as its RPF neighbor on the route to the source.

   [SwitchB] ip rpf-route-static 50.1.1.100 24 20.1.1.2
   

# Display RPF information for Source on Switch B.

[SwitchB] display multicast rpf-info 50.1.1.100
 RPF information about source 50.1.1.100:
     RPF interface: Vlan-interface101, RPF neighbor: 20.1.1.2
     Referenced route/mask: 50.1.1.0/24
     Referenced route type: multicast static
     Route selection rule: preference-preferred
     Load splitting rule: disable

The output shows the following information:

• The RPF route on Switch B is the configured static multicast route.

• The RPF neighbor of Switch B is Switch C.