What would happen if I set up an IP on the loopback interface and make it the querier address? Would that work as is...or will I have to enable routing and then multicast routing for it to work on all the vlans?

No, I wouldn't think you need to enable routing and multicast routing, but as to usage of a loopback as the querier address, the documentation is a bit unclear whether the loopback might be considered the global address in "If there is no IP address configured on the VLAN interface, the IGMP snooping querier tries to use the configured global IP address for the IGMP querier."

Thinking in unicast terms, "Configure an IP address on the VLAN interface. When enabled, the IGMP snooping querier uses the IP address as the query source address." makes sense, but multicast isn't unicast, so with IGMP queries, a loopback address might work fine, but I don't have first hand experience to say so with 100% certainty.

Ok thanks.

I set up the querier to be the IP on the SVI of the mangement vlan...I think it's working but I won't know 100% till tomorrow morning...I'll let you know.

Thanks!

Joseph

Must admit my first thought was to enable an IGMP querier but i was confused as to why without it things stopped working.

If you are running IGMP snooping but not with a querier then as far as i am aware this should make no difference and the multicast traffic is just treated as broadcast traffic by the switch.

Any ideas as to why running IGMP snooping broke the server communication ?

Jon

Jon,

Without seeing or testing what's going on, I can only hazard a guess, but I suspect IGMP snooping without a IGMP querier might be behaving somewhat like a flood and prune multicast protocol that doesn't see any responses to IGMP queries and times out sending to the subnet. Although in this case, unlike multicast routing, time outs are the individual ports. In other words, the server clients announce the multicast group join, which IGMP snooping detects and opens their port for multicast, but without a periodic IGMP query and response for the IGMP snooper to detect, the snooper then believes the multicast client has silently left the multicast group (IGMPv1) and then blocks the port for that multicast.

[edit]

When I say open or block a port for multicast, of course, it's really whether the switch will replicate the multicast frame/packet for that port.

Ok so so far it seems to be working...all the servers are getting data.

However...when I do a show ip igmp snooping querier detail it shows the admin state as disabled...does that mean igmp snooping is not enabled on these vlans and multicast is still acting as broadcasts??

Here's an example (I masked the IP):

Vlan 500: IGMP switch querier status

--------------------------------------------------------

admin state : Disabled

admin version : 2

source IP address : *.*.*.*

query-interval (sec) : 60

max-response-time (sec) : 10

querier-timeout (sec) : 120

tcn query count : 2

tcn query interval (sec) : 10

operational state : Disabled

operational version : 2

tcn query pending count : 0

"However...when I do a show ip igmp snooping querier detail it shows the admin state as disabled...does that mean igmp snooping is not enabled on these vlans and multicast is still acting as broadcasts??"

Unsure. If might be because there isn't an external querier detected on that VLAN or that you're not using a VLAN IP for the querier IP. What do show ip igmp snooping and show ip igmp snooping groups display?

sh IP IGMP Snoopig shows that igmp snooping is enabled on those vlans...and show ip igmp snooping groups shows a bunch of groups and port lists associated with them...which I'm guessing means that IGMP snooping is actually working...