snoop_cache_unresolved

[herve_colasuonn]

hi,
we have a stack with X460-G2 in summitstack.
EXOS is running in 15.6.3.1 v1563b1-patch1-8
The stacks has 6 members, with 2 uplink 10Gb/s to Cisco Core.
I think we have multicast problem : in logs, i have :
Slot-1: exosSnoop: snoop_cache_unresolved:851: snoop_cache_unresolved failed to send report
What does it mean ?
Anyone know that ? how to correct it ?

Thx for your help.
Regards,

[herve_colasuonn]

Hi Etherman,

i don't know what is the muticast traffic. We don't do multicast deployement actually. So, only windows computers, or VDI products, does multicast. But i don't know how they do multicast. I think with U-p'n'p, bonjour, or something like that.

The only things, is when i hace the log message snoo_cache_unresolved, one of the slot in my stack takes 90 to 100% CPU. Then the slot reboot or failed, and the stack becomes unstable.

So i think i have multicast problems on my networks, but i don't know how to treat it. Only because leak of CPU on SummitStack X460-G2. In our last campus, we have Cisco 2950 or 2960, with same architecture, without any multicast problem.

It seems like the satck wants to treat multicast traffic, but i use the stack in L2 only. Ans maybe the stack wants to do some L3 with multicast.

Or i'm totally wrong. Actually, the most likely is multicast problem, maybe multicast loop. But i'm not sure. Only leak of cpu on stacks... And i don't how how can i have multicast loop, without any multicast configuration !

[EtherMAN]

If you disable IGMP snooping all mcast will be treated like a broadcast packet and send to all ports in each vlan. We run 1800 or so vlans in our Metro network and only have igmp snooping enable at edge switches as a rule. Only exception to that is we do have one vlan in our core that is IPTV traffic and at peak it hits 1.4 Gbs so we do keep it enabled so we don't overrun any one gig aggregation links coming off the core. By have it enabled it only runs about 650 Mbs in the core. So to answer your question is two fold. How much mcast traffic is in each vlan? If not that much then in our experience with a lot of vlans in one switch it is better to disable IGMP snooping globally and go back and enable it as needed. I would guess since you are running in Spars Mode there is not much Mcast traffic in any one single vlan ??

[herve_colasuonn]

That's what i wanted to do in the first time...
But what are the consequences ? If i disable igmp on many (or all) vlans, what happend when a computer will ask multicast with Bonjour, or Up'n'p ? Does it flood all the stack to reach a multicast router on the cisco core ? And at last, is igmp necessary on L2 network ?
So sorry for thoses questions, but i'm not familliar with multicast.

Thx ,

[Bill_Stritzinge]

I would assume you have a ton of vlans..? To disable snooping on a per vlan basis use the command "disable igmp snooping vlan " - I would look for the vlan that has the most streams or ones that you do not need.