Re: 400G link L2 flakiness over DWDM

[Tom Beecher <beecher () beecher cc>]

> One tantalizing
> clue was another customer using Cisco Nexus had better results after
> they enabled "link transmit reset-skip"
> (https://quickview.cloudapps.cisco.com/quickview/bug/CSCvi45168).  Not
> clear exactly what that option does, and there doesn't seem to be an
> obviously equivalent config knob in Junos.


I have a vague recollection of that option being there to basically ignore
certain events that would normally cause link drop in order to keep an
unstable link up.  It was a long time ago, I sent a message to the guy I
used to work with who might remember more.

On Fri, Jan 10, 2025 at 3:00 PM Oliver Garraux <oliver () g garraux net> wrote:

> We have a number of new 400G provider waves with odd flakiness that we
> can't seem to sort out.
>
> These links appear good - light levels are fine, links will be up with
> working LLDP.  But if we admin down / up the link on the IP side, many
> of them won't come back up on their own.  Our provider sees "loss of
> alignment" alarms on the optical equipment, and we can eventually get
> the links back up if they bounce them a few times on the DWDM side.
>
> We're using Juniper PTX's, with Juniper 400G FR4 and 400G LR4 optics.
> Same issue on different circuits/devices/paths with this provider, but
> no issues with other transport providers using the same optics on our
> end.  Believe our provider is using Ciena optical equipment.
>
> Has anyone seen issues like this before?  Our provider has been
> looking into this for months without much progress.  One tantalizing
> clue was another customer using Cisco Nexus had better results after
> they enabled "link transmit reset-skip"
> (https://quickview.cloudapps.cisco.com/quickview/bug/CSCvi45168).  Not
> clear exactly what that option does, and there doesn't seem to be an
> obviously equivalent config knob in Junos.
>
> Thanks,
> Oliver