[nsp] ospf over tunnels

[Ryan O'Connell]

On Wed, 11 Sep 2002 10:43:20 -0700 (PDT) Mark Kent <mark@noc.mainstreet.net> wrote:
> I've got remote site 1 on a DS3 with MTU 4470
> and remote site 2 on a fastethernet with MTU 1500.
> 
> I have a GRE tunnel between them, with a cisco7206vxr
> on each end, 12.0(21)S on each router.
> 
> I can't run ospf between the two because of this:
> 
> Sep 11 10:35:46: OSPF: Rcv DBD from x.y.z.w on Tunnel0 seq 0x8C9 opt
> 0x42 flag 0x7 len 32  mtu 4446 state EXSTART
> Sep 11 10:35:46: OSPF: Nbr x.y.z.w has larger interface MTU
[snip]
> If I change the MTU on my DS3 to 1500 then what happens
> to the 1514 MTU on the tunnel?

It's the MTU on the tunnel interface that's the problem, not the MTU on the
physical interfaces. Set the MTU on both tunnels to be the same and it
should work.

-- 
      Ryan O'Connell
Mail: ryan@complicity.co.uk
  CV: http://www.complicity.co.uk/ryancv.pdf
      CCIE #8174