Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
Community Member

All ports off, but switch still on -- what could cause?

I have a 3750 POE SwitchStack, and one of the switches in the stack today had all the ports down on it.

The switch itself was on, fan going, I could run commands on it.

But trying to go into an interface and shut/no shut had no effect.

When I rebooted the switch, all the ports came back to life.

Anyone have any ideas what could cause this, and/or what diagnostics to run?




VIP Super Bronze

Are you collecting logs for

Are you collecting logs for your switches? If you are sending logs to a syslog server, take a look there for any clues. Also, never reboot before looking at the log file on the switch itself. One more thing, take a look at the flash and look for a crash file.



Community Member

No, not sending off to a

No, not sending off to a syslog server at the moment. That would be smart... Good point about not rebooting before looking at the logs. I didn't realize rebooting flushed the logs, but running the 'show log' command looks like that's the case. Anything I can look at with the logs flushed?

VIP Super Bronze

keep an eye on the processor

keep an eye on the processor "sh proce cpu" I would also read the release notes for the specific version of IOS you are running and look for bugs that might be causing the ports to shut down. Keep checking the log file on the switch itself for any error messages.  Set up a syslog server and the send the logs to it. It can save you lots of headache.




Community Member

Try to disconnect it switch

Try to disconnect it switch from stack, connect console cable to PC, power off and then power on swtich, and view boot log (diagnostic e.t.c.)

------------------------------------------------------ Helping seriously ill children, all together. All information about this, is posted on my blog
CreatePlease to create content