[c-nsp] Switch lights rapid blinking

[Aaron]

Sh int | in 5 min

Look for high numbers

Or clear counters then do " Sh int | in 5 min" see if you have rapidly
increasing numbers could indicate forwarding loop or jabbering device....
perhaps look for lots of one direction in or out but not opposite direction.
If you find a strange port shut it down and perhaps see what lights do

"Sh proc cpu his"  --- is it high?

Sh log - mac flapping?  Perhaps enable mac-move

aaron


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Jeffrey G. Fitzwater
Sent: Monday, January 28, 2013 2:09 PM
To: <A.L.M.Buxey at lboro.ac.uk> 
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Switch lights rapid blinking

Alan, there are many normal things that can cause this, like ARP broadcast,
unknown unicast especially in a large flat nets.

   I  would start there, but remember it might be normal.


Jeff Fitzwater
OIT Network Systems
Princeton University
 wrote:

> Hi,
>> Can someone please point me in the right direction to correct this issue.
I came into a network that is using the default vlan and for about 2 weeks
now, every switch and port is rapidly blinking.  I looked at wireshark and
don't seen anything out of the ordinary.  I also checked for loops in the
network and don't see any.  Is there some tool I can use to track down what
is causing this?  I'm running cisco 2960's all over.
> 
> if all the usual things are okay - ie spanning-tree is stable, there 
> are no links going up/down, you have eg portfast for edge devices etc 
> etc then perhaps all you are seeing are the usual busy lights for 
> cisco LEDs - what sort of rapid blinking? all blinking at same time?  have
you done a port-mirror of the uplink to see what is really going on?
> 
> alan
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