I don't think the router needs to be configured to be in any multicast group
in order to process the membership report. A router is registered for a
multicast group if it receives a membership report for that multicast group.
These membership reports can be unsolicited or in response to membership
query.
In IGMP v1, a router will periodically multicast a membership query with the
GDA set to 0.0.0.0. A host from all active multicast groups will send a
report in response to the query.
In version 2, a router can direct the membership query to a specific group,
by setting the GDA to the group's address.
The router uses membership reports to maintain its multicast table. Groups
are added to the table (or refreshed) when membership reports are received,
and existing groups are removed from the table, if no membership reports are
received for that group.
CM
-----Original Message-----
From: R.Srikanth
To: [EMAIL PROTECTED]
Sent: 05/07/01 14:39
Subject: Question about IGMP queries and reports [7:11062]
Hi,
I have a question about IGMP queries and reports.
1. When an IGMP querier router sends a query, this packet is sent to
224.0.0.1
address (01-00-5e-00-00-01) to which all multicast capable hosts listen.
2. When a host sends a membership report (either in reponse to the
query, or
an unsolicited report ) for the group in which it is a member ( say
224.1.1.1), the report is sent to the 224.1.1.1 address. This is the
address
specified in the 'Group address' field of the IGMP report message, as
well as
the destination IP address of the IP packet carrying this report. The
Ethernet frame that encapsulates this packet would carry the destination
Layer-2 multicast address of 01-00-5e-01-01-01. This method ensures
report
suppression by other hosts which are members of the same group, as they
will
listen to this address and suppress their reports.
The querying router has to pick this frame and look into the IGMP report
to
know that the host is or wants to be a member of 224.1.1.1 group. Does
it
mean
that router is also a member of this group inorder to pick this frame
and
process the report message ?
If another host is a member of a different group 224.1.1.2 and sends
report
to this address, should the router listen to this address also to
process the
reports for this group ?
How will the router to know what groups it should listen to, so that it
can
process the report messages to find out what groups are active ?
What method does the router use, if this is not the correct one ?
Thanks,
Srikanth.
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=11072&t=11062
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