SG300-xx Multicast broadcasting

[Robert Blake]

We're setting up a multicast video network using a series of SG300 switches using 1.2.7.76.  We're currently testing two SG300-10s, but are finding that the switch with the cameras connected to it are broadcasting the multicast traffic to all ports.  We started by assigning each switch a unique IP address within VLAN 1, the only VLAN.  We enabled Bridge Multicast Filtering and set the Forwarding Method to IP Group Address on both switches.  Next, we enabled IGMP Snooping for each switch and also for VLAN1.  On the switch connected to our server, we also enabled the Querier.  The other switch, which connects to our multicast sources broadcasts all the multicast traffic.

From here, we tried enabling the Querier on both switches with them set to Auto.  They seem to work out which is the master Querier without issue.  This seemed to fix the problem until we rebooted both switches.  The switch with the video source is broadcasting multicast traffic.  The switch connected to our server appears to be working fine.  Settings were all verified as having been saved prior to the reboot. 

Bonjour is disabled as I recall seeing something about that in the release notes.

Any ideas as to what we've missed?

[Tom Watts]

Hi Robert, try to specify one of the ports as a mrouter port connecting between the switches.

-Tom
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[Robert Blake]

I checked the Multicast Router Port settings on the secondary switch and it correctly has Port 10 set as Dynamic.  I tried changing it to Static, but as suspected, this did not seem to have an effect.

[Robert Blake]

Looking closer at the settings in the switch that is broadcasting multicast traffic, I see that the multicast group being broadcast does not appear in the IGMP/MLD IP Multicast Group page.  From what I've been reading, this means that the multicast group is not properly registering in the switch without the Querier running.

[Tom Watts]

Hi Robert, you have to have at least 1 querier. If you set up several queriers, there is an election process and only one will function per subnet, which may make an undesirable result. My interpretation is you are using a 'main switch' as your mrouter. The main switch has to transmit the join messages. When using IGMP/MLD, that switch will forward the multicast frame to all ports that are registered to receive the multicat stream uaing the IGMP join messages.

So, first notice, when using IP multicast group, there is a drop down box for each VLAN. The system maintains a lists of multicast groups for each vlan and it is what manages the multicast information that each port should receive.

-Tom
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[Robert Blake]

Perhaps a diagram or two will help.

This is where we started.  Not shown is a pair of laptops running wireshark, one on each switch.  The problem was that the secondary switch was broadcasting everything from the encoder instead of just passing it to the main switch for the server.  We then enabled the querier on the secondary switch.  According to the VLAN status, the querier was still disabled (due to the election).  However, the broadcasting stopped.  When we rebooted both switches, the multicast started broadcasting on the secondary switch again.  Our next step was to insure we had the current firmware and disabled Bonjour.  A few reboots later, and we're still where we started.

The group table from the main switch shows all the multicast groups.  The server is GE1 and the secondary switch is GE10.

The same table from the secondary switch only shows two groups.  The missing group which is broadcasting from our video encoder is 224.16.17.7.  When it was working, this group properly appeared in the seconday switch with G10 as the only included port.  G10 is the port used to link to the main switch.

[Tom Watts]

What happens if you make the "secondary switch" the querier instead of the "main switch"?

-Tom
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[Robert Blake]

When we have the querier running only on the secondary switch, the multicast traffic stops broadcasting on both switches.  Rebooting the switches seems to work as well.  I've added an encoder to the main switch so that we have one on each.  It appears to be working fine this way.  I've rebooted the switches in different orders to see if I can break it.  So far, it seems to work.

So, the question is... what's wrong with the main switch that it isn't properly managing the multicast traffic as a querier.

I suppose the next step is to factory reset both and start over to see if there was an odd configuration in the main switch.

[Tom Watts]

Hi Rob, also remember, although the switch can be a querier, it is not a fully functional one... there are limitations

-Tom
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[Robert Blake]

I remember seeing that, but not what the limitations are.  Is there a particular model we can use with a fully functional querier?

[Robert Blake]

I've tracked down a Catalyst 3560-24PS and will try using that as I see it functions as an IGMP Proxy/PIM, which is what I am seeing is required to make our architecture work.