Errdisable issue

[orkhan.rustamli.96]

Hi, everyone!

I have had and interesting issue today. We had to give internet service to one of the customers, so we put one cisco switch (SF220 Small Bisuness) and one router (800 series). Fiber Optic cable is connected to switch via SFP module, Switch is connected to router and then again router and router shares internet to LAN. However despite everything was connected and configured correctly the router couldnot access internet. I thought the reason of problem was SFP module (i may not be supported by switch). For checking it i made a loop with one short optic patch cord. Switch gave me this log: Link is up, Link is in errdisable state, Link is down.

My question is: Doesn`t the interface have to stay on err-disable state? Why did it converged to down state?

Thanks beforehand!

[shaps]

The down state was a byproduct of the err-disabled issue.  all it was saying was the link is down now as the port has efficiently been shut down logically by the switch protecting it self from potential loops

[orkhan.rustamli.96]

Well.. Then let me ask you isn`t err disable protection state either? If i am not mistaken the principle of err-disable is putting interface in non-working state with any shutting down and etc. So doesn`t err disable state protect from loops either? Another Point is you mentioned "has efficiently been shut down logically". However interface status was notconnected.

[cofee]

It should stay in err-disable state until someone clears it using shut-no shut command or there is a policy configured on the switch to clear err-disable state. No traffic will traverse interface that's in err-disable state until the error-state state has been cleared and the underlying issue is resolved. I think it stays in that state so the network operator will know that the error has occurred during port negotiation/frames rx tx

[orkhan.rustamli.96]

Thank you for your helpful information. I also know that it should stay in err-disable state. However in my case(When i created little loop on switch by one patch cord(Connecting to tx rx of SFP same patch cord)) it first went to err-disable and immediately turned to down state. I am interested why it changed to down? Should not it stay in err-disable state until administrator manually change it or err-disable recovery takes it turns?

[cofee]

It appears err-disable recovery feature is not supported on the switch you are using and therefore it doesn't stay in that state, but that doesn't make much sense to me.

Please use the commands below and share the output ( you may not get any out if this feature is not supported):

* sh int status err-disabled

* sh errdisable recovery