[c-nsp] Switch lights rapid blinking

[Jeffrey G. Fitzwater]

I would configure a port on the switch with all the blinking lights, with just a pc attached that is capable of tcpdump.  Do not configure it as MONITOR port.

!. Does this port blink the same as others (approx.)?

If so then the packets that are arriving at this port (inbound) are being sent there because they are broadcast, multicast, or unicast unknown.

2. Does the switch FDB have a very short aging timer or did it get set to "0" (macs are NOT stored in FDB and all ports in that vlan get hit with every packet).  Most CISCOs support this now.   You would only use this if you know what your doing.   (like the vlan is just passing from one port to another as an example).


Jeff F.

On Jan 28, 2013, at 3:51 PM, Michael Sprouffske wrote:

I don't see high cpu on any switch.  Traffic seems to flow just fine.  I'm not sure if the ports did this the whole time or if this started one day.  Its hard to say if there has been a change.  This network needs to be rebuilt with proper vlans and removing a /16 from this 200 host network.


________________________________
From: "A.L.M.Buxey at lboro.ac.uk<mailto:A.L.M.Buxey at lboro.ac.uk>" <A.L.M.Buxey at lboro.ac.uk<mailto:A.L.M.Buxey at lboro.ac.uk>>
To: Jeffrey G. Fitzwater <jfitz at Princeton.EDU<mailto:jfitz at Princeton.EDU>>
Cc: Michael Sprouffske <msprouffske at yahoo.com<mailto:msprouffske at yahoo.com>>; "cisco-nsp at puck.nether.net<mailto:cisco-nsp at puck.nether.net>" <cisco-nsp at puck.nether.net<mailto:cisco-nsp at puck.nether.net>>
Sent: Monday, January 28, 2013 12:50 PM
Subject: Re: [c-nsp] Switch lights rapid blinking

Hi,

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

as I said, it could be the usual blinking...they do blink a lot even in
a test/lab environment... and checking whats going on on uplink
might be key for flat network checking. the checking counters/processor etc
that was also mentioned is useful.

alan