causes of down/down

alxx

Trying to list all the reasons for down/down on a switch port,
think I've missed a couple

speed mismatch
device on other end not powered or in fault
device on other end has interface down
cable not connected at one end or other
bad cable
wrong cable(not auto crossover/audo mdix not enabled)

Excellent1

I'd toss in the various switchport security violations for consideration. If it's placed in shutdown mode, it will show down/down (err-disabled). Of course, at that point, the port has to be manually shut and reopened (unless you've got the auto-recovery setup).

Also, I'm pretty sure that if you have an incorrect etherchannel setup, you'll have a down/down for channel configuration mismatch.

Anyway, I'm sure the experienced folks can chime in with some better feedback.