loop check on Enterasys C5K125-48

[giro]

Hi all.
Is there an easy way to do a check on a C5K125-48 about possible loops on network?

Tnx

[Bill_Handler]

Giro, a few questions...

Do you have NetSight available?

How many Enterasys Switches/Stacks are on the subnet in question?

Is STP enabled?

There is likely a CLI command that would show the full port statistics. You could run the command, copy the output into an excel sheet and sort for the highest non-unicast packet count as mentioned above.

Why do you think there's a loop in the network to begin with?

[giro]

OK tnx.
In this case there's not CDP available on the network and I was looking for some less empirical tests.
I tried some commands to display if my PC MAC address was learned by more than 1 port on the switches but I have not prominent results...
Any other suggestion?

[Bill_Handler]

The easiest way we've found is to use the 'show neighbor' command. If you see the switch you're connected to on more than 1 port (excluding ports associated with lags), you know you have a loop with one of those ports.

For an instance where you don't have CDP available, it gets a little more difficult. We recently had a customer that had a loop on a commodity switch that was connected to an Enterasys Stack causing a broadcast storm in their network. The CPU utilization for the switch stacks on the subnet was at 70+%. We looked at the port statistics in NetSight Console. We looked at the port (non-uplink port between stacks) with the highest non-unicast packet in count, and disabled that port. We noticed the CPU utilization drop to normal levels almost immediately. For us, we got the problem port on the first shot. It may take a little trial and error, but I think you'll be able to find a loop with this method if CDP is not available.