[c-nsp] ISIS MTU Ignoration good/bad???

[Matthew Walster]

On 26 June 2013 16:07, Adam Vitkovsky <adam.vitkovsky at swan.sk> wrote:

> Hi folks,
> I have just recently noticed that newer ISIS implementations actually
> ignore
> interface MTU discrepancies.
> I was relying on the local interface MTU comparison against the IIHs size
> to
> discover any MTU inconsistencies.
> I believe there should be a knob to enable/disable MTU comparison same as
> there's currently a knob to turn on/partially-off/off(XR) the IIH padding.
> I'd like to know the opinion of the community on this matter please.
>

AIUI, IS-IS does not insist on MTUs being identical on either side of the
link. It was only OSPF that screwed this up.

What I think you're mentioning is that Cisco did hello-padding so that an
IS-IS frame (once received) could only be processed if it met the buffer
size on both sides -- it's documented here:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00801e1e2b.shtml

M