[j-nsp] QSA adapters and MTU

[Ola Thoresen]

On 03.11.2023 16:04, Chris Wopat wrote:

> We use them on MX304 at 10g, primarily to get DWDM SFP+ to work. MTU 
> is fine, it's 9k as a part of LACP on a recent deployment. The adapter 
> simply passes through lane :0 to the port when configured as QSFP+. If 
> you insert the adapter and no optic, the device is unaware of its 
> existence - you only see the SFP+ info.
>
This is the same use case as for us, and my understanding is exactly 
that they are just passing a single lane through, and should not really 
know anything about packets or ethernet frames or anything.

But still - people more knowledgeable than me - assure me that there is 
a limit of 2008 Bytes MTU - at least for 1G.

I just can't find this documented anywhere, and I would have thought 
that more people would have made more fuss about it when they start 
using it if this is a real issue.


> We haven't tested in prod on 1g but i think we did in the lab. can 
> probably toss something in there if you're really curious. I think the 
> juniper supported optic page lists QSA adapter support or not. I 
> thought it was generally supported with Junos 20+ nowadays.
>
Yes. They list QSA adapter as supported, also for 1G optics, and don't 
write anything about any MTU limitations in the Hardware Compatibility Tool.


/Ola (T)