[c-nsp] MTU / BGP

Mark Tinka mark.tinka at seacom.mu
Tue Jul 21 02:55:23 EDT 2015


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256



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.
-----BEGIN PGP SIGNATURE-----
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=eMKi
-----END PGP SIGNATURE-----



More information about the cisco-nsp mailing list