IGMP Snooping

Hi, Can any one plz tell me about

the difference between

IP Layer IGMP Snooping & Layer 2 IGMP Snooping

Thanks ....

Reply to
vicky
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IGMP snooping is done by a L2 device peeking up at L3. It's described in RFC 4541.

If the device is a L3 router, and it's doing IGMP, then it's not called "snooping." It's basic IGMP.

Bert

Reply to
Albert Manfredi

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Reply to
vicky

no (or it doesnt have to be) - 2 different functions.

really, read the RFCas Bert suggested - they are meant to be relatively painless, and there is usually a good summary / intro

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Reply to
Stephen

The router port is not the same as the root port, necessarily.

RFC 4541 page 4 says:

The switch supporting IGMP snooping must maintain a list of multicast routers and the ports on which they are attached. This list can be constructed in any combination of the following ways:

a) This list should be built by the snooping switch sending Multicast Router Solicitation messages as described in IGMP Multicast Router Discovery [MRDISC]. It may also snoop Multicast Router Advertisement messages sent by and to other nodes.

b) The arrival port for IGMP Queries (sent by multicast routers) where the source address is not 0.0.0.0.

The 0.0.0.0 address represents a special case where the switch is proxying IGMP Queries for faster network convergence, but is not itself the Querier. The switch does not use its own IP address (even if it has one), because this would cause the Queries to be seen as coming from a newly elected Querier. The 0.0.0.0 address is used to indicate that the Query packets are NOT from a multicast router.

c) Ports explicitly configured by management to be IGMP- forwarding ports, in addition to or instead of any of the above methods to detect router ports.

Bert

Reply to
Albert Manfredi

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