[c-nsp] MTU / BGP

[Mark Tinka]

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On 21/Jul/15 08:43, Gert Doering wrote:
>
> Side note - if you have a network where path mtu discovery fails and BGP
> sessions die as a consequence, something in your network is seriously
broken.
>
> Normally, even if MTUs on different links are different, pMTU discovery
> gets it sorted out nicely.
>
> Typical issues that are very much a recipe for trouble is when you have
> a single layer2 network where different devices have different layer 3
> MTUs.  Always ensure that *all* adjacent L3 devices agree on the
> IP/IPv6/MPLS MTU (and take into account the subtle differences between
> IOS, IOS XR and JunOS...).

The problem is MTU discovery when you're leasing your Layer 2 network.
I've had issues with this, which is why I've had to disable that
capability in past jobs, due it being global but some of your leased
Layer 2 services have MTU issues.

If you run your own dark fibre network, then MTU discovery is easier.
But since you do, you probably don't need it in the first place :-).

Mark.
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