Re: How to filter external OSPF routes from database ?

Hi, I viewed the video but still can not filter external routes. I built the
lab in dynamips exactly as shown in the presentation (5 mins 30 sec):

R1------area1-----R2-----area0------R3--------area2--------R4

R1 advertises 1.0.0.0/8 into area1.
On R3 I added static route "ip route 1.0.0.0 255.0.0.0 Null0"

All works as expected: 1.0.0.0/8 will not show on R4.

But if R1 redistributes 1.0.0.0/8 with command "redistribute connected
subnets" then the route 1.0.0.0/8 will show show as E2 on R4. R4 will not be
able to ping 1.1.1.1 but it still shows in the routing table.

My question is then, how to prevent external route redistributed in Area1
from showing in any other area.

> > Hi,
> >
> > Take a look at the following free class on demand and you will master
> that
> > topic in minutes:
> >
> >
> http://www.micronicstraining.com/videos/filtering-ospf-prefixes-section-1.zip
> >
> > HTH,
> > --
> > Piotr Matusiak
> > CCIE #19860 (R&S, SEC)
> > Technical Instructor
> > MicronicsTraining.com
> >
> > If you can't explain it simply, you don't understand it well enough -
> > Albert Einstein
> >
> >
> > 2009/11/9 Tomasz Solski <tom.solski_at_gmail.com>
> >
> > > 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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> >
> >
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> >
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>
>
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>
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Received on Tue Nov 10 2009 - 11:37:56 ART