RIP Justification

Mark Smith nanog at
Thu Sep 30 04:57:32 UTC 2010

On Thu, 30 Sep 2010 14:13:11 +1000
Julien Goodwin <nanog at> wrote:

> On 30/09/10 13:42, Mark Smith wrote:
> > One of the large delays you see in OSPF is election of the designated
> > router on multi-access links such as ethernets. As ethernet is being
> > very commonly used for point-to-point non-edge links, you can eliminate
> > that delay and also the corresponding network LSA by making OSPF treat
> > the link as a point-to-point link e.g.
> > 
> > int ethernet0
> >   ip ospf network point-to-point
> > 
> > 
> > If your implementation doesn't support point-to-point mode for an
> > interface, point-to-multipoint mode on an ethernet would achieve
> > something somewhat equivalent.
> Do any implementations go point-to-point automatically if an ethernet
> has a /30 or /31 mask?

Don't know.

If you want to see what interface model OSPF is using, on a Cisco you

show ip ospf interface <blah>

The interface type for loopback interfaces can be a bit surprising and
the consequences a bit unexpected if you're intentionally or
otherwise not using a /32 prefix length on one.


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