Cisco IOS Cookbook, 2nd Edition

Static Multicast Routes and Group Memberships

Problem

You want to override the dynamic multicast routing and group membership with static entries.

Solution

By default, PIM will use the same dynamic routing table learned by the unicast routing protocol. However, in some cases you don’t want to use these routes. For example, you might have to send multicast traffic through a tunnel to bypass a section of network that doesn’t support multicast routing. In this case, the unicast routing table is clearly the wrong path for multicast traffic. So you need to specify a different route for multicast traffic to use:

Router1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#ip multicast-routing
Router1(config)#ip mroute 192.168.15.0 255.255.255.0 192.168.98.6
Router1(config)#interface Tunnel0
Router1(config-if)#ip address 192.168.98.5 255.255.255.252
Router1(config-if)#ip pim sparse-dense-mode
Router1(config-if)#tunnel mode gre ip
Router1(config-if)#end
Router1#

You can specify a static IGMP join to ensure that the router always thinks that there are group members on an interface:

Router1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#ip multicast-routing
Router1(config)#interface FastEthernet0/0
Router1(config-if)#ip pim sparse-dense-mode
Router1(config-if)#ip igmp join-group 239.5.5.55
Router1(config-if)#end
Router1#

Discussion

The static mroute command is used only to describe the Reverse Path Forwarding ...