From: CCIEin2006 (ciscocciein2006@gmail.com)
Date: Thu May 18 2006 - 14:05:17 ART
From what I can tell, RFC 2236 states the Group Specific Query is actually
sent to the destination IP address of the group, not 224.0.0.1.
This is a table from the RFC:
9. Message destinations
This information is provided elsewhere in the document, but is
summarized here for convenience.
Message Type Destination Group
------------ -----------------
General Query ALL-SYSTEMS (224.0.0.1)
Group-Specific Query The group being queried
Membership Report The group being reported
Leave Message ALL-ROUTERS (224.0.0.2)
On 5/18/06, Tony Paterra <apaterra@gmail.com> wrote:
>
> Reading Beau's multicast book and I can't get a clear understanding of
> what happens when a multicast listener leaves a group in IGMPv2 (yes
> I'm sorry I'm slow)... If you have RouterA as the IGMP Query Router
> and a Host H1 on an Ethernet interface that is part of the multicast
> group 224.1.1.10... My understanding is when H1 wants to leave the
> group:
>
> 1. It sends a Leave Group message with the destination in the IP
> packet of 224.0.0.2 (All Routers) w/ the Group Address field set to
> 224.1.1.10
> 2. The IGMP Query Router responds by sending a Group Specific Query
> to 224.1.1.10 to see if there are still any active listeners out there
> (who will respond with a Membership Report if they exist).
>
> My question is what the packet looks like for the Group Specific
> Query. What is the IP destination of that packet? My guess is that
> it's 224.0.0.1 (All Hosts) with the Group Address of the IGMP layer
> set to 224.1.1.10. Sorry, don't really know how I could simulate this
> with debugs, etc... :-).
>
> Thanks in advance,
> --
> Tony Paterra
> apaterra@gmail.com
>
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