Configuring Advanced

Features

 

 

Configuring Advanced Features

Multimedia Traffic Control with IP Multicast (IGMP)

IGMP is configured on switches 3 and 4. Either of these switches can operate as querier because a multicast router is not present on the network. (If an IGMP switch does not detect a querier, it automatically assumes this role, assuming the querier feature is enabled—the default—within IGMP.)

Switch 1

IGMP is NOT

Running Here

 

 

 

 

 

 

 

 

 

 

 

IGMP IS

 

 

 

 

 

 

 

 

 

 

 

Running Here

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Switch 3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Multicast

 

 

 

 

 

 

 

 

 

 

 

Data Stream

Switch 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IGMP IS

 

 

 

 

 

 

 

 

 

 

 

Running Here

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PC 2

 

 

Switch 4

 

 

 

PC 1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PC 5

 

PC 6

 

 

 

 

 

 

Figure 9-68. Isolating IP Multicast Traffic in a Network

In the above figure, the multicast group traffic does not go to switch 1 and beyond because either the port on switch 3 that connects to switch 1 has been configured as blocked or there are no hosts connected to switch 1 or switch 2 that belong to the multicast group.

For PC 1 to become a member of the same multicast group without flooding IP multicast traffic on all ports of switches 1 and 2, IGMP must be configured on both switches 1 and 2, and the port on Switch 3 that connects to Switch 1 must be unblocked.

9-100