[c-nsp] IP MTU setting + OSPF

[Mikael Abrahamsson]

On Mon, 21 Dec 2009, Chris Wopat wrote:

> I'm changing MTU on some 7200s with PA-FE's to 1530 with the "mtu
> 1530" command on the interface. To get OSPF to neighbor with a 2800
> (no user settable MTU), I've put "ip mtu 1500" on the 7200. In my
> testing this works fine. Does this in any way prevent the 7200 from
> generating an OSPF packet that's larger than 1500 and potentially
> breaking things down the road? The following links have been helpful
> for MTU descriptions but I'm not seeing the answer to this question in
> there.

If you set "ip mtu 1500" then indeed it will not send any IP packets 
larger than 1500, and since OSPF runs over IP, this is also affected.

But yes, you're doing the right thing (if the "mtu 1530" command is 
because you're running MPLS or something else non-IP that needs a higher 
MTU).

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se