Allied Telesis AR400 manual Stopping snoopers from snooping non-IGMP messages

Stopping snoopers from snooping non-IGMP messages > Example

Stopping snoopers from snooping non-IGMP messages

Some networks include routers that have no interest in IGMP, but still generate multicast messages by running protocols like OSPF. When a Snooper receives multicast messages from such a router, the Snooper adds the router’s port to its All Groups port list. This means the router is unnecessarily sent IGMP and multicast traffic. Using IGMP features to prevent the excess traffic is particularly helpful when you cannot or do not want to control the traffic at the router.

This example describes how to use AlliedWare’s advanced IGMP features to prevent this behaviour, by limiting the ports that the Snooper adds to the All Groups list, or by stopping particular types of traffic from adding ports to the All Groups list.

Example

The example is based around a network that has a router running OSPF. The router is connected to a LAN through a switch. The LAN is a single subnet with no OSPF routers inside it. The network for this example uses the same loop as for "IGMP snooping" on page 9, with a router attached to switch 2. The network is shown in the following figure.

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

Switch 3: Snooper

igmp-all-groups.eps

We used an AR410 router, but the router configuration works on any AR400 or AR700 series router.

Each example in this section modifies the following base configuration.

Page 86 AlliedWare™ OS How To Note: IGMP