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Page 86 | AlliedWare™ OS How To Note: IGMP
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.
We used an AR4
1
0 router, but the router configuration works on any AR400 or AR700
series router.
Each example in this section modifies the following base configuration.
Multicast Server
AT-8948
Switch 1:
Querier
Rapier 24i
Switch 2:
Snooper
Client 1
Rapier 24i
Switch 3:
Snooper
Client 2
port 1
port 2
port 3
port 25 port 25
port 26 port 26
port 50
(blocked by STP)
port 49
port 24
Router
OSPF
OSPF
OSPF
igmp-all-groups.eps