[nsp] OSPF over RBE - no full adjacency

[Gert Doering]

Hi,

On Thu, Jan 22, 2004 at 10:52:35AM +0300, Alexey G Misurenko wrote:
> > did you change the MTU on the main interface on the ATM side to 1500?
> > if not the default MTU there is 4470.
> 
> it is not necessary to change MTU, will be enough to set
> 
>   ip ospf mtu-ignore
> 
> in  interfaces configuration

In this specific setup, *not* changing ip mtu will lead to packet losses
as soon as you have a packet larger than the ethernet MTU and want to send
this to the ATM VC (because the ethernet bridge (!) at the other end 
will not be able to send it, and being a bridge, can't fragment it either).

As long as all your packets come in from other ethernet interfaces, you're
save, but you can see the problem if you run an extended ping with
2000-byte packets from the ATM router itself.  (Or if a packet came in
from a POS or ATM interface with big MTU on both sides).

"mtu mismatches hurt"

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
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