[c-nsp] IGMP on 6500s - %MCAST-xx-GC_LIMIT_EXCEEDED

[Phil Mayers]

Tim Stevenson wrote:
> It refers to Layer 2 group MAC entries (try sh mac- mul ig or sh 
> multicast group); these are driven by IGMP join activity in host VLANs.

Ok, I setup an EEM applet to "show mac- multicast igmp" and append to a 
file when this message occurs, and there does not look to be a very 
large number of layer2 MAC group entries - 197 in fact.

What else can I do / add to the EEM to try and diagnose the source? 
Debug of IGMP join activity is unlikely to be do-able on this router.

FYI, the EEM I'm using is:

event manager applet check-mcast-fdb
  event syslog occurs 1 pattern "MCAST-.*-GC_LIMIT_EXCEEDED"
  action 0.9 cli command "enable"
  action 1.0 cli command "show clock | append disk0:igmp"
  action 1.1 cli command "show mac-address-table multicast igmp | append 
disk0:igmp"

(EEM rocks by the way...)

> 
> You actually can't increase past 15K & still get L2 mcast constraint for 
> the additional groups.

I wouldn't expect to get to anywhere near that, which is why I'm trying 
to track down the cause - something is going awry I suspect.

Note this is on 12.2(18)SXF2 and the only really out-of-ordinary things 
it's doing is HSRP for a lot of layer3 interfaces and VRF lite.