Re: How to filter external OSPF routes from database ?

I am not sure if there is any condition associated with the task. With the
provided info, I think, you can configure A1&2 as normal areas, and use "ip
os database-filter all out" on R2's interface connected to R3.

On Wed, Nov 11, 2009 at 3:31 PM, Tom Solski <tom.solski_at_gmail.com> wrote:

> It works in my lab too. On R2 there is a config which filters out route
> 1.0.0.0 from being propagated into Area 0:
>
> <<<
> area 1 nssa no-summary
> summary-address 1.0.0.0 255.0.0.0 not-advertise
> >>>
>
> So far the only way I found to filter external routes out of an area is to
> convert it to NSSA. In the same time area 1 will not see any outside
> routes...
>
> So let me define the new challenge, just for the heck of it:
>
> R1------area1-----R2-----area0------R3--------area2--------R4
>
> R1 redistributes external network 1.0.0.0/8 into area1.
> R4 redistributes external network 4.0.0.0/8 into area2.
>
> Route 1.0.0.0 must be visible only inside area 1 (i.e. on router R1 and R2
> only)
> Route 2.0.0.0 must be visible on ALL routers in the domain.
>
> Is that possible ?
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of S
> Malik
> Sent: 11-Nov-09 11:02
> To: Tom Solski
> Cc: Miroslav Kosut; Cisco certification
> Subject: Re: How to filter external OSPF routes from database ?
>
> Tom,
> I checked,if area is nssa, then you can filter either on actual ASBR or ABR
> by using the same cmd (pl test and verify). in ASBR case, it take lsa
> type-7
> out from DB and at ABR it takes lsa-5 out of database but lsa-7 still
> remains in DB which means that nssa will have this route and rest of the
> areas will not. If we run it on actual ASBR then whole ospf domain will not
> have the routes which were re-distributed.
>
>
>
> On Tue, Nov 10, 2009 at 7:27 PM, Tom Solski <tom.solski_at_gmail.com> wrote:
>
> > Thanks Miroslav. Summary address on R2 works if area 1 is configured as
> not
> > so stubby (NSSA). I am referring to this topology:
> >
> > R1------area1-----R2-----area0------R3--------area2--------R4
> > R1 redistributes external 1.0.0.0/8 into area1.
> >
> > IOS appears to me really inconsistent here. Why summary-address works for
> > N2
> > routes and does not for E2 routes?
> >
> >
> > -----Original Message-----
> > From: Miroslav Kosut [mailto:miroslav.kosut_at_gmail.com]
> > Sent: 10-Nov-09 16:22
> > To: Tomasz Solski
> > Cc: Cisco certification
> > Subject: Re: How to filter external OSPF routes from database ?
> >
> > Stubby area :-)
> >
> > External LSAs (LSA5) can be filtered on ASBRs using summary-address
> > NET MASK not-advertise. I don't know about any other way of filtering
> > them on ABRs except using stubby areas.
> >
> > Regards,
> > Miroslav
> >
> > On Nov 10, 2009, at 10:15 PM, Martin Hogan wrote:
> >
> > > What does the Cisco Doc tell you about that command?
> > >
> > > Hint: It's only effective on a particular LSA type.
> > >
> > >
> > >
> > > On Tue, Nov 10, 2009 at 7:44 AM, Tomasz Solski
> > > <tom.solski_at_gmail.com> wrote:
> > >
> > >> How to filter external OSPF routes from database ?
> > >>
> > >> Here is an example:
> > >>
> > >> R1------Ar0------R2------Ar1-------R3
> > >>
> > >> R1 redistributes routes into Area 0.
> > >>
> > >> I want ot configure R2 so R3 does not have a specific external
> > >> route in its
> > >> database.
> > >>
> > >> I tried on R2:
> > >> <<<
> > >> ip prefix-list R1toR3 seq 5 deny 1.1.12.0/24
> > >> ip prefix-list R1toR3 seq 10 permit 0.0.0.0/0 le 32
> > >> router ospf 1
> > >> area 1 filter-list prefix R1toR3 in
> > >>>>>
> > >>
> > >> but it looks like external routes can not be filtered with filter
> > >> list. As
> > >> soon as I advertise 1.1.12.0/24 on R1, instead of redistributing
> > >> it, it
> > >> disappears from R3's database and routing table.
> > >>
> > >>
> > >> Blogs and organic groups at http://www.ccie.net
> > >>
> > >>
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Received on Wed Nov 11 2009 - 22:55:34 ART