On 23 July 2016 at 10:28, Tore Anderson <t...@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