IS-IS on FRR - Is Anyone Running It?

Mon Apr 6 09:16:06 UTC 2020

On 6/Apr/20 11:05, Saku Ytti wrote:

> And the only thing this 'ISIS MTU' (think you mean CLNS MTU)...

Yes, I mean "clns mtu".

>  does, is
> for some cases make ISIS hellos larger. If you don't pad ISIS hellos,
> or if you have standard compliant ISIS, it doesn't do anything past
> 1500B.

Agreed.

But in the network devices, IS-IS will infer the interface MTU to setup
adjacencies. It doesn't matter what it is, it just needs to either be
the same or low enough for the interface to support it.

> More accurately ISIS doesn't have a way to fragment LSP into two LSP,
> so the whole ISIS network needs the same LSP-MTU, which has nothing to
> do with 'clns mtu', LSP-MTU does not increase with increasing CLNS
> MTU. There is no utility of having a harmonised CLNS MTU,...

Do you run CSR1000v on ESXi?

>  so if you
> want to speak to FRR, you can just do 1500B and it's fine.

Which is what this whole thread is about. How do I set that, manually,
without changing the physical interface MTU?

Mark.