Re: [magma] Question about IGMP host implementation

Bharat Joshi <> Wed, 12 October 2011 11:24 UTC

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From: Bharat Joshi <>
To: Kunal Shah <>, "" <>
Date: Wed, 12 Oct 2011 16:49:55 +0530
Thread-Topic: Question about IGMP host implementation
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Subject: Re: [magma] Question about IGMP host implementation
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Hi Kunal,

        I think to keep the security tight, it is better to not respond to queries received from a source address which does not fall on a subnet on that interface. Please note that this should be done only broadcast interfaces. It may not work on point-to-point links.

        If you look at the security consideration in RFC 2236, it is mentioned that for reports, the above check should be done.

From: [] On Behalf Of Kunal Shah []
Sent: Wednesday, October 12, 2011 6:08 AM
Subject: [magma] Question about IGMP host implementation

Hi all,

Can an IGMPv2 host respond to a general query originated from a subnet other then its own?? RFC 2236 states:

""query received" occurs when the host receives either a valid
     General Membership Query message, or a valid Group-Specific
     Membership Query message.  To be valid, the Query message must be
     at least 8 octets long, and have a correct IGMP checksum.  The
     group address in the IGMP header must either be zero (a General
     Query) or a valid multicast group address (a Group-Specific Query)"

There is no requirement for the source address to be on the same subnet as the host.


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