UDLD problem on Denali 16.3.x

[sbrobak]

Have problem with uplink port on remote switch going in udld err-disable when connected to 3850 running 16.3.3

Looks very similar to CSCvd33197

Denali: 3850 Uplink port goes down after reload due to udld err-Disable on remote end

But looks like the CSC is Cisco internal.

Someone with experience and workaround?

[Julio E. Moisa]

Hi

UDLD is used to find unidirectional traffic problem, have you certified the link? Replace the patch cords and SFP on each end, if the problem persists you can certify the link to discard any problem with the cabling. 

[sbrobak]

Link and SFP+ is ok. If I disable udld on the the 3850 sfp port, the link is up. Still up when I try to enable udld again. I have not tried to boot the switch to see what happens.

[Leo Laohoo]

Try downgrading the IOS of the switch to 3.6.6 or 3.7.5.

[youknownothing]

I have had this issue too on 16.3.3. The workaround that worked for me was disabling UDLD at global and enabling it per interface. There is something wrong with the automatic mechanism of UDLD when the device reboots. Pcaps show that it is sending/receiving UDLD frames on both sides, but the device simply is ignoring them and goes into unknown state.