Link flaps when connected through 10G DWDM Circuit

[kozharov]

Hello team,

We have a problem with link flapping between Cisco switches which are connected via 3rd party DWDM network: Switch  <--> 10G DWDM <--> Switch

Initially these were N7K switches. Such behavior was known and there is a work around for it ( https://bst.cloudapps.cisco.com/bugsearch/bug/CSCur11844/?referring_site=bugquickviewclick ).

We increased the link debounce timer and it helped perfectly.

Now we have another problem, one of the switches connected to N7K through DWDM network is 3850 switch. Now the link flaps again, but there is no such option as debouce timer on 3850 switch. Carrier-delay option also doesn’t help.

The question is what can be done on 3850 switch to increase debounce timer to make 10G link through DWDM system be stable.

I really appreciate your advice!

Best regards,

Michael

[Georg Pauwen]

Hello,

is there anything in the logs of the 3850 indicating why the link is flapping ? You might want to toggle 'downshift/no downshift' in interface configuration mode and check if that makes a difference...

[kozharov]

Hello and sorry for late reply,

I can’t display logs as 3850 was eliminated from the path and now again DWDM connects two Nexus switches. We again increased default debouce timer on Nexus switches from 100ms to 200ms and everything works fine.

As we know the debounce timer delays notification of a link change. If we increase it on the switch and make it more than 100ms everything works fine.

So the question remaines the same if it is possible to increase debounce timer on 3850? I’m 100% sure this will solve the problem and make 10G link through DWDM system work stable in the case we use 3850 switches.

Thank you!