IGMPV3: Disabling IGMPV3 processing since MMLS was enabled on MSFC

mbhnt · ‎01-19-2010

We have a network consisting of 30+ 3550 and 3750 switches which each connect back to 2 6509's, both with MSFC's.

Each wiring closet has it's own L2 VLAN with routing taking place on the 6509 MSFC. Some VLAN's are trunked to all the Wiring Closets for various reasons (most noteably the LWAPP vlan's for our LWAPP WLAN)

Earlier today multiple switches were disconnected from the network because their GBE uplink ports went into error disable. We can't pinpoint the reason for this (there were no changes made to the network) and the only clue I can find is that around the same time one of the 6509's sent the message "IGMPV3: Disabling IGMPV3 processing since MMLS was enabled on MSFC" to the syslog server.

My initial reaction is that there's a spanning tree problem or possibly a loop on the network. This was further backed up by the fact that many devices also complained about duplicate IP Addresses being identified.

Can anyone explain what the IGMPV3 message is and why it might occur?

Thanks

Reza Sharifi · ‎01-19-2010

Hello,

It seems that you can not have IGMPv3 and MMLS enabled at the same time:

from the 6500 command reference guide:

IGMP version 3 processing and the multicast multilayer switching (MMLS) feature cannot be enabled at the same time. To enable IGMP version 3 processing, you must disable MMLS from the Multilayer Switch Feature Card (MSFC). If you attempt to enable IGMP version 3 processing when MMLS is enabled, a warning displays to indicate that IGMP version 3 processing will be enabled after MMLS is disabled from the MSFC.

Here is more info:

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/catos/7.x/command/reference/set_f_l.html

HTH

Reza

mbhnt · ‎01-20-2010

Thanks, I've actually seen that page when I was looking into the problem yesterday and understand what the message means.

What I don't understand is why this message would be displayed when we hadn't made any IGMPV3 or MMLS changes.

The switch seems to have made the configuration change itself for some reason. Are there any circumstances which could cause a switch to make these changes?? There's only 3 people who have access to the switch so I'm pretty sure it wasn't made by an engineer...