Hi,

 I setup a full mesh LAG between 4 switches, a pair of stacked 6224s and a pair of stacked 8024f. My config was running fine for 2 weeks, but suddenly over the weekend I came across an issue where I could no longer ping between the two management switches in each stack. None of my config has changed, but all of sudden the communication failure was evident. To resolve this, I simply removed the trunk cables and then used a single cable to connect the two switch stacks (previously my port channel was using 4 cables).

A small snippet of the RAM logs:

Notice NOV 02 17:06:48 TRAPMGR Spanning Tree Topology Change Received: MSTID: 0 Po1 

  Notice NOV 02 17:06:46 TRAPMGR Spanning Tree Topology Change Received: MSTID: 0 Po1 

  Notice NOV 02 17:06:16 TRAPMGR Spanning Tree Topology Change Received: MSTID: 0 Po1 

  Notice NOV 02 17:06:14 TRAPMGR Spanning Tree Topology Change Received: MSTID: 0 Po1 

  Error NOV 02 17:01:21 DRIVER ATP: TX timeout, seq 58794. cli 778. to 1(mac a4:ba:db:7b:e0:75) tx cnt 21.

  Error NOV 02 16:46:23 DRIVER ATP: TX timeout, seq 58355. cli 778. to 1(mac a4:ba:db:7b:e0:75) tx cnt 21.

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Any advice on how to find out what the root cause failure is would be much appreciated - like I said, the config was running fine for 2 weeks. The switches I'm using are running a firmware that's about 3 years old!

Thanks