Okay, enough talk.
Let's watch this conversation in action on the live network.
First, I'll check to see which groups the client has currently joined.
Because this isn't a Cisco iOS class, I won't focus on the exact commands,
but rather the output.
The client is currently requesting multicast for 239.1 .1 .1 and 239.2 .2 .2.
When the router sends a query asking the client who wants multicast,
the client should respond with two IGMP membership reports,
one for each group.
Let's switch over to the Globomantics router.
This device should issue a query,
so let's enable IGMP debugging and wait for that event.
I'll specifically target group 239.1 .1 .1 just to cut down on the output.
Okay, we see the IGMP v1 query sent out towards the clients.
A short time later, the client sends an IGMP v1 report for group 239.1 .1 .1.
The Globomantics router goes on to update its multicast routing table,
or MRT, with this new multicast entry.
Some of the other terminology here, such as group record and exclude,
will be explained in detail as it becomes relevant,
so don't worry.
I'll finish up by checking the router to ensure it knows
about both 239.1 .1 .1 and 239.2 .2 .2,
which should have been reported from 10.1 .4 .4,
the Globomantics client.
Okay, I see both groups reported from the proper client address. Let's analyze these IGMP packets next.