Archive for August, 2013

Posted by keith.wirch at August 9, 2013

Category: Weird Fixes

So me and the network engineer at work had been working on something that was causing us both grief.  I had enable Wake on Lan for all my Dell T1650 Laptops.  It was working great! Magic Packet (mc-wol) was working fine.  Problem was with with Port Security.

When the station were Shutdown or Hibernating we were getting random port security issues.  Only when they were in this state though.  We “wiresharked” the traffic and found that the stations were sending MAC address advertisements of 00:00:00:00:00:00.  There might an “on” bit here and there but really it was just sending garbage!  Well since this garbage looked like a MAC address to the switch, Port-Secuirty on the switch shut the port down.  This would be flagged on our syslog server and we’d have to restart the computer only to later have it happen again a few weeks later.  I really seemed random.  It was popcorning throughout the network.

So we tried updating the BIOS.  Our thought was “Well it is happening when the computers were off.  Probably not an OS level issue”. That didn’t fix the issue.  But we did get shiny new BIOS’s.  Yay!?!

So we hemmed and hawed trying to think of something.  Then we finally started looking at the OS level.  We thought… maybe the drivers?  Turns out, we were right (finally).  The NICs were all Intel NICs so we grabbed the updated drivers from the Intel site.  We then updated the drivers on all the T1650 workstations.  It’s been over a month now and not one of our over 300 has thrown MAC garbage to trigger port security.  I guess when the stations were shutting down, the OS does some voodoo with the NIC to keep it alive during shutdown and that is why the drivers fixed it?  I dunno.  I do know that our syslog server is seeing much better days.  Unless the NE takes down the Core switch again!  hehe.

I hope this helps some other poor sysadmin who has port security issues with these stations.  Hope you found this post via Google.  Cause Google wasn’t really helping us.