[j-nsp] mx960 to mx960 via ciena 6500 - mtu smaller in the middle

[Lukas Tribus]

Hello Aaron,


On 16 April 2018 at 21:58, Aaron Gould <aaron1 at gvtc.com> wrote:
> See juniper interface MTU is set to max 16000 bytes. but when I ping I can
> only get 9584 bytes through to the other side of the link.  This mx960 is
> linked to another mx960, but Ciena 6500 dwdm is in between the mx960's.
>
>
>
> Is there any reason why I should be concerned that currently Ciena tells us
> that they only support 9600 byte MTU and that I have 16000 set on my MX960's
> ?
>
>
>
> Is there an issue that could arise with this scenario ?

I don't see how you can still ask this question, given that you just
triple posted OSPF/MTU problems to nanog/c-nsp/j-nsp lists back in
November for this exact reason:

http://seclists.org/nanog/2017/Nov/150
https://lists.gt.net/cisco/nsp/198415
https://lists.gt.net/nsp/juniper/63232


What is the reason you keep rejecting the fact that inconsistent and
wrong MTU configurations have an actual impact?

The MTU has to be correctly configured, period. It is really as simple
as that. And no, you do not workaround MTU problems with commands like
"ignore-mtu". You configure the MTU correctly.



lukas