Configuring IP Multicast Routing

Configuring IP Multicast Routing
When configuring multicast, keep in mind that many options and protocols can be configured.
This is why it is so important that you have previously prepared and planned for the actual configuration.
It isn’t something that you can just sit down and throw together (not without a lot
of problems, anyway).
Configuring routers for IP multicast is different from enabling CGMP on switches. You must
also remember that switches do not understand Internet Group Management Protocol (IGMP)
by default, and that you need to enable multicasting on switches and routers for hosts to be able
to subscribe to a multicast group.
Configuring IP Multicast Routing 621
This section of the chapter covers the basics of configuring multicast on routers and switches.
It also covers the configuration of rendezvous points. This is a very important task because without
a rendezvous point, you will not be able to send or receive multicast packets across a network.
We also cover the individual interface configurations on routers. CGMP processes are discussed
in a little more detail than in the preceding chapter. Later, we will describe the multicast settings
that can be made on a multicast-enabled router (and switches). The following sections “Enabling
IP Multicast Routing” and “Enabling PIM on an Interface” describe required configuration,
whereas the configuration described in the rest of this section is optional.
It is best to prepare a configuration task list before setting out to configure a group of routers.
The configuration list should be specific to the device that will be configured. That fact makes it
hard to present a set list of configuration tasks that would apply to all scenarios. However, two
items definitely must be configured on a router in order for multicast to even begin working:
enabling multicast routing and enabling PIM on the interfaces that will carry multicast traffic.