Re: OSPF default route multiple processes

In this case both OSPF process are treated as different routing protocol
instances so the router is going to compare de AD of both to select the
best route, in case of a tie like in this escenario its going to select the
one learned first.

Because of this it could work like you expect for a while but a convergence
on the network could change the behavior.

You could change the AD of one of the process to force it to use the
default you want

Regards

Jose

On Fri, Jul 26, 2013 at 11:24 AM, Kristian Francisco <kristian.j.f_at_gmail.com
> wrote:

> Hey Marc, I would like to take a stab at your questions, but will let some
> of the CCIEs with more experience confirm. I would expect the following to
> take place:
>
> Although there are two ospf processes running, there's only one routing
> table. I would not expect ospf to treat its rules on route selection
> differently. (this is an assumption). For true segmentation, consider vrfs.
>
> As you mentioned, the type-1 LSA to be preferred over a type-2 LSA. Once
> you make the default routes both of the same type, the following selection
> criteria will apply:
>
> - If type-2 metric is the same, prefer route with better internal cost.
> - Directly from RFC: In any case, among the remaining routing table
> entries, select the routing table entry with the least cost; when there
> are
> multiple least cost routing table entries the entry whose associated
> area
> has the largest OSPF Area ID (when considered as an unsigned 32-bit
> integer) is chosen.
>
> Best Regards,
>
> Kristian J. Francisco
>
>
> On Fri, Jul 26, 2013 at 10:20 AM, Marc La Porte <marc.a.laporte_at_gmail.com
> >wrote:
>
> > Rati,
> >
> > How does it choose between the two processes though?
> >
> > Cheers,
> > Marc
> >
> > On Fri, Jul 26, 2013 at 7:12 PM, Rati Berikaant Jokhadze
> > <iinfo83_at_gmail.com>wrote:
> >
> > >
> > > On 07/26/2013 08:50 PM, Marc La Porte wrote:
> > >
> > >> 1. What is the order of operation within OSPF to select default routes
> > >> from
> > >> different processes?
> > >>
> > >> 2. How do I ensure the border router ALWAYS takes the default route
> from
> > >> Area 51 (although it has multiple default routes from Area 0 in it's
> > >> database)? Since OSPF metric-type 1 has preference over metric-type 2,
> > do
> > >> I
> > >> change the metric-type in Area 51 to type 2 and ensure it's always
> lower
> > >> than from Area 0?
> > >>
> > > 1. First recieved route within process
> > >
> > > 2. I dont think so , that you can do this , someone will answer
> > exactly...
> >
> >
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-- 
Atentamente Jose Zamora Prado
Telefono 8252885
Blogs and organic groups at http://www.ccie.net