L2 Configuration changes to enable Multicast Routing?

[Brian Maxwell]

I have an L2 network with Multicast in use for security cameras.  Due to some upcoming video integrations, there is need to enable Multicast routing (Customer equipment will do routing).  My L2 core switch is acting as Multicast Querier currently and this is the only configuration pertaining to IGMP on the switch:

ip igmp snooping querier
ip igmp snooping vlan 1100 mrouter interface Te1/0/1

Field switches point back to this switch's IP as the querier.

Should there be any need for configuration changes to get Multicast routing functional?  I do not know what the customer has configured for Multicast routing but they're thinking I may need to change PIM settings on the L2 switches.

Thanks!

[Richard Burts]

We do not know much about your network or about your customer. But what we do know is that multicast IP is a layer 3 function. PIM is a layer 3 protocol. I have a hard time seeing how any change would be needed if your network is truly a L2 network, other than perhaps some tweaks to IGMP.

[Brian Maxwell]

It certainly solidifies what I already believed. Thank you.

[Giuseppe Larosa]

Hello Brian,

the only possible change is related to the igmp snooping querier that is needed only when there is no multicast enabled router / multilayer switch (otherwise for lack of IGMP queries and IGMP reports the snooping function would block the traffic).

However, this setup is vlan specific per vlan if you are going to dedicate a new Vlan to this new customer you don't need to change anything in the current used Vlan(s).

I had a very strange case with electromedical devices that were using IPv4 related multicast MAC addresses but the traffic was not IPv4 multicast (it was not IP at all). To be able to make this traffic to  flow we had to disable IGMP snooping on that VLAN.

Hope to help

Giuseppe

[Joseph W. Doherty]

Unsure your switch would need any PIM related settings, unless you've trying to implement PIM snooping (not to be confused with IGMP snooping).

As to IGMP snooping, you may want to deactivate your switch being the IGMP querier, as that function is normally done by the (multicast) router. I'm unsure how the switch might impact the multicast router if it's the IGMP querier. (If the switch blocks IGMP replies from all active receiving hosts, the multicast router will stop sending off local network multicast.)

[Brian Maxwell]

I thought about this too. Would I remove the reference to the querier in all of the switches that are currently pointed to it?
Or would I point them at the newly configured router?

[Joseph W. Doherty]

Good question (which means I'm unsure of the answer). I think (?) it should work if you remove all those references, but I recall (?) that some IGMP snooping implementations can work a bit "better' if they "know" which of their ports leads to the querier.