Extremely high utilzation on sc0 interface of 6500

[cat6506]

Greetings,

Anyone ever seen an sc0 interface of a 6506 switch reach a ridiculously high level of utilization??

This switch acts as the primary root bridge for a single vlan flat network. Sup. Engine - SUP1-2GE. There are 2 stackable 3500's (Switches A and B) connected via fiber and all have relatively simple configs purely for the use of network connectivity.

The user population is nominal with no bandwidth intensive applications present.

Network problem that existed was the following:

-Monitoring system catches the sc0 interface of core switch running at a utilization level far exceeding it's normal rate.
-At this time, users connected to switch A experience an intermittent loss of connectivity with a 50-60% packet loss rate.
-Users connected to switch B appear to have no problems with connectivity and 0% packet loss rate.

Assuming that hardware is not the issue here...
Has anyone had a similar experience??
If so, can you provide any insight as to what the problem could've been??

Thanks,

 

[vipergg]

The SC0 interface should not be in any of the user vlans .You should have a separate subnet to use to manage your switches if you don't already have . You don't indicate if these are all in the same vlan or are they broken up ? This could be almost anything , I have seen one infected machine bring a 6500 to it's knees before . What's the utilization on the 3550 that the people are having trouble on ? Have you checked the links for errors and made sure you don't have any loops in your network though if spanning tree is configured correctly it should take care of any loops.

 

[cat6506]

A new implementation for segmented user vlans is in effect but, cannot be done until after the new year.

For this particular situation now... It is a single vlan, flat network.. All switches and users reside on vlan 1...

The utilization for that 3500 was at 60% cpu level.. high, but, not killing the switch..

The switchports themselves though were maxing out utilization levels.. anything connected had a 5 min. output rate of over 2000 packets/sec. And this was for a laptop not even running any apps. but, simply plugged into the network.

Problems seems to just fix itself after a prolonged period of time..
Now.. assuming that all nodes on the default mgmt. vlan 1 will be changed... Is it safe to say that because of this setup, it causes the network to go haywire..

Thanks for the input..