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UCS Code Upgrade: 24 Seconds Explained

There was a lot of interest in my last post about our code upgrade.  What stood out to many (as well as us) was the 24 second disruption in network traffic on each fabric interconnect side when it was rebooted.  Meaning I upgrade the B side and when that fabric interconnect goes into its reboot all of the Ethernet traffic (remember the fiber channel traffic had NO issues) that was talking on the B side is disrupted for 24 seconds.

The answer was in my core 6513 configuration regarding spanning tree.  I would like to thank Jeremiah at Varrow and the guys at Cisco who helped us figure this out. 

Turns out that one of the first configuration confirmation items in the code upgrade process (really it should have been setup all along . . .) was making sure the port channels that the fabric interconnects are connected to are set with spanning-tree portfast trunk.  An email was sent to get this confirmed and configured but it got missed, to bad it was not in the Cisco Pre-Requisite document as a reminder.  What this command gives you is if and when the trunk port link to the fabric interconnect goes away for any reason the 6513 will not go through the normal spanning tree timers and quickly allow the traffic to flow on the remaining path (in our case the remaining connection to the fabric interconnects).

We have now enabled spanning-tree portfast trunk on our port channels and should be positioned now to eliminate that pesky 24 second Ethernet disruption that impacted some of the traffic.  Details, details!

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May 1, 2010 Posted by | Cisco UCS, UCS Manager | , , | Leave a comment