Q: How do I view and clear err-disabled switchports on a 3550?

A:

On the 3550, the command #sho int status will print a table of interfaces, with status. The status may be "err-disabled". To investigate such ports, use #sho int status err. To clear the port status, issue a (c-i)#shut and then a (c-i)#no shut on the interface. Or, you can enable autorecovery after a time period. Use these commands to check your current autorecovery config:

#sho errdis detect
#sho errdis flap-val
#sho errdis recovery

To enable autorecovery for a particular cause, use

(c)#errdis recov cause {cause}