MTU

Sat Jul 23 10:17:30 UTC 2016

On 23 July 2016 at 10:28, Tore Anderson <tore at fud.no> wrote:

> * Baldur Norddahl
>
> > What is best practice regarding choosing MTU on transit links?
> >
> > Until now we have used the default of 1500 bytes. I now have a
> > project were we peer directly with another small ISP. However we need
> > a backup so we figured a GRE tunnel on a common IP transit carrier
> > would work. We want to avoid the troubles you get by having an
> > effective MTU smaller than 1500 inside the tunnel, so the IP transit
> > carrier agreed to configure a MTU of 9216.
>
> You use case as described above puzzles me. You should already your
> peer's routes being advertised to you via the transit provider and vice
> versa. If your direct peering fails, the traffic should start flowing
> via the transit provider automatically. So unless there's something
> else going on here you're not telling us there should be no need for
> the GRE tunnel.
>

I did not say we were doing internet peering...

In case you are wondering, we are actually running L2VPN tunnels over MPLS.

Regards,

Baldur