Re: 3750 stack port flapping periodically

CHRISTINE BERNS · ‎10-11-2010

Hello,

We have a stack of six 3750 switches. Periodically, the switch stack logs a message indicating that the stack port on one side or the other of the stacking cable or on both sides simultaneously, goes down, then one second later comes up:

Oct 10 22:43:46: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 4 has changed to state DOWN
Oct 10 22:43:46: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 3 has changed to state DOWN
Oct 10 22:43:47: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 4 has changed to state UP
Oct 10 22:43:47: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 3 has changed to state UP
Oct 11 02:44:11: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 4 has changed to state DOWN
Oct 11 02:44:12: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 4 has changed to state UP

.

Oct 11 10:47:22: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 4 has changed to state DOWN

Oct 11 10:47:23: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 4 has changed to state UP

Oct 11 12:49:32: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 3 has changed to state DOWN

Oct 11 12:49:33: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 3 has changed to state UP

We have replaced the stack cable between switch 4 stack port 1 and switch 3 stack port 2, but the messages continue. This switch stack had been up for over a year without incident, then after a power shutdown event in the building caused the switches to lose power, the messages started coming up a few hours after power was restored to the stack. Are there any debug commands or other troubleshooting tips that would assist us in determining which switch is at fault?

the-lebowski · ‎10-11-2010

Here you go:

SW-CORE#debug platform stack-manager ?
  all    Stack Manager All
  rpc    Stack Manager RPC use
  sdp    Stack Manager Discovery Protocol
  sim    Stack Manager Information Module
  ssm    Stack Manager State Machine
  trace  Trace Stack Mgr Function Entry and Exit

Good stacking info: http://www.techcity.cgngroup.com/2010/10/stacking-cisco-catalyst-3750-switches/

Have you tried shutting down all the switches, replacing the cable and them powering them all back up? Backplane might have gotten fried...do you have a ciscos support contract?

andtoth · ‎10-11-2010

Hi,

What is the model number of the switches? You can find this information from 'sh ver'.

What IOS version are you running?

Andras