IGMP Snooping

IGMP Snooping
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Subject Author Date
IGMP Snooping vicky 06-02-2008
---> Re: IGMP Snooping Albert Manfredi06-02-2008
Posted by vicky on June 2, 2008, 8:17 am
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Hi,
Can any one plz tell me about

the difference between

IP Layer IGMP Snooping
& Layer 2 IGMP Snooping


Thanks ....

Network Magic Graduation 20% off animated banner
Posted by Albert Manfredi on June 2, 2008, 10:42 am
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> =A0 Can any one plz tell me about
>
> =A0 the difference between
>
> =A0 =A0 =A0IP Layer IGMP Snooping
> =A0 & =A0 Layer 2 IGMP Snooping

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

Posted by vicky on June 6, 2008, 3:08 am
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>
> > =A0 Can any one plz tell me about
>
> > =A0 the difference between
>
> > =A0 =A0 =A0IP Layer IGMP Snooping
> > =A0 & =A0 Layer 2 IGMP Snooping
>
> 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

----------------------------------------------------------------------------=
--


Hi ,

Can any body please tell me how the router port(for IGMP Snooping
case ) is selected among all ports in a layer 2 switch

Is router port is same to root port (formed by STP)

Thanks................

Posted by Stephen on June 6, 2008, 2:47 pm
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On Fri, 6 Jun 2008 00:08:50 -0700 (PDT), vicky

>>
>> >   Can any one plz tell me about
>>
>> >   the difference between
>>
>> >      IP Layer IGMP Snooping
>> >   &   Layer 2 IGMP Snooping
>>
>> 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
>
>------------------------------------------------------------------------------
>
>
>Hi ,
>
>Can any body please tell me how the router port(for IGMP Snooping
>case ) is selected among all ports in a layer 2 switch
>
>Is router port is same to root port (formed by STP)

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
www.ietf.org
>
>Thanks................
--
Regards

stephen_hope@xyzworld.com - replace xyz with ntl

Posted by Albert Manfredi on June 7, 2008, 5:56 pm
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> Can any body please tell me how the router port(for IGMP Snooping
> case ) =A0is selected among all ports in a layer 2 switch
>
> Is router port =A0is same to root port (formed by STP)

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



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