how to set priority of routers in ospf

[Martin Kraus]

On Tue, Oct 27, 2009 at 11:09:46PM +0100, Ondrej Zajicek wrote:
> Really, in the case of a tie, shorter way will be used. I omitted this case
> for simplicity.
> 
> There is a simple explanation: consider there is just one metric, which
> is a triple (K, M2, M1), where K is a kind of a route (0 for I, 1 for
> E1, 2 for E2), M2 is ospf_metric2 for E2, zero for others and M1 is
> ospf_metric1. Then the route with smaller triple is preferred (the
> triples are lexicographically ordered).
> 
> > One (hopefuly) final question. How does bird determine what route to designate
> > as E1? All I've got from bird are either E2 or Internal routes.
> 
> If external route is exported to OSPF, you can set ospf_metric1 or
> ospf_metric2 using filters.
> 
> If just ospf_metric1 is set, route becomes E1.
> If just ospf_metric2 is set, route becomes E2.
> If nothing is set, E2 with ospf_metric2 = 10000 is the default.
> If both are set (uninteresting corner case), ospf_metric2 is ignored.

Great. Now it makes sense to me. I've read through the various documentation, even
rfc(log time ago), but it never made much sense and I've never needed to know
how the metrics really work until now. 

thanks for the clarification
mk