Allied Telesis AR400 manual Igmp snooping, Example, AlliedWare OS How To Note Igmp

IGMP snooping > Example

IGMP snooping

In this example, we discuss IGMP snooping, the key to efficient multicast traffic flow in a layer 2 network. IGMP snooping is enabled by default on switch ports in Allied Telesis managed layer 3 switches and routers—it does not require any configuration.

In a single-switch network, IGMP snooping makes multicasting happen with no configuration at all. All you need to do is connect your server and clients to the switch.

In a multi-switch network, at least one switch must also have an IGMP configuration. This switch is called the IGMP Querier and coordinates the flow of multicast information through the network. The following example describes a multi-switch configuration, so as well as discussing the effect of IGMP snooping, it outlines the actions that the Querier takes. "Multiple potential IGMP queriers" on page 15 discusses the role of the Querier in greater detail.

Example

This example has a 3-switch loop, as shown in the following figure. One of the switches is running IGMP and the other two switches are running IGMP snooping.

	Multicast Server
	port 1	AT-8948
			Switch 1:
			Querier
	port 50	port 49
	(blocked by STP)
	port 26		port 26
Switch 2:	Rapier 24i		Rapier 24i	Switch 3:
Snooper	port 25		port 25	Snooper
	port 2		port 3
	Client 1		Client 2
				igmp-snooper.eps

Page 9 AlliedWare™ OS How To Note: IGMP