CCIE Wireless Multicast Best Practices

Here are some best practices for multicast with wireless.

First thing make sure multicast is enabled on the switch:

• Switch(config)#ip multicast-routing distributed

There are two flavors of multicast dense mode or sparse mode.  Dense mode is a push and prune method where you just enable multicast on which interfaces you want to participate and all of those interfaces are pushed the multicast stream.  If you want to enable that use the command:

• Switch(config-if)#interface vlan 100
• Switch(config-if)#ip pim dense-mode

Most people use sparse mode and this is most likely what you will see on the exam.  With pim-sparse mode you need a rendezvous point where all the multicast is directed where you can joing the multicast group.  There are different ways to configure this but for the interfaces to use multicast you use the commands:
  

• Switch(config-if)#interface loopback 0
• Switch(config-if)#ip pim sparse-mode 

To create a rendezvous point you use the following command:

• Switch(config)#ip pim rp-address 10.10.10.10

Most users use a loopback address as the rendezvous point.  You can also add access-lists after that command with the access-list number to limit what groups can join or deny.

You can also use Auto-RP so instead of using a static rendezvous point, a router can advertise itself as a RP.  You need a RP mapping agent to listen to other routers RP's to decide which should be the RP.  
You can use the following command:

• Switch(config)#ip pim send-rp-announce loopback 0 scope 6 group-list 1
• Switch(config)#ip pim send-rp-discovery loopback 0 scope 6

The scope means how many hops you want to announcement goes. In this example it is 6 hops.  The group list is an access-list for what multicast groups can join this rendezvous point.