From: David Luu (wicked01@xxxxxxxxxxxxx)
Date: Fri Jun 28 2002 - 21:28:09 GMT-3
forgot to add...
2 ospf processes on R3
At 07:35 PM 6/28/2002 -0300, Carlos G Mendioroz wrote:
>David,
>how do you "block" routes in an OSPF link ?
>
>David Luu wrote:
> >
> > sounds simple enough...
> >
> > use route tags
> >
> > have R2 set a tag for the 10.1.0.0/16 and have R3 block the tag going into
> > area 0
> >
> > At 09:10 PM 6/28/2002 +0100, Peter Whittle wrote:
> > >Selectively blocking OSPF routes between areas
> > >----------------------------------------------
> > >
> > >I would like to pose a simple scenario to the group.
> > >
> > >There are 4 routers R1 .. R4
> > >
> > >R1 is injecting routes into RIPv2 say 10.1.0.0/16
> > >
> > >R2 is running RIPv2 on e0, it is also connected by e1 to OSPF Area 1 and
> > >must inject the routes learnt from RIP into AREA 1. There are other
> > >routers also connected to the ethernet segment in Area 1 again running
> > >OSPF. The routes injected by R2 into area 1 must be visible to these
> > >routers via OSPF.
> > >
> > >R3 has 2 ethernet interfaces e0 in OSPF Area 0, and e1 in OSPF Area 1.
> > >It must see the RIP routes injected into OSPF by R2 (ie 10.1.0.0/16).
> > >
> > >R4 in connected to the ethernet in Area 0 and is also running OSPF and
> > >is outside of your control.
> > >
> > >STOP the RIP routes that were injected by R2 from being seen in Area 0.
> > >(i.e. block the 10.1.0.0/16 route)
> > >
> > >You may only program routers R2, & R3 to achieve this.
> > >
> > >
> > >Any thoughts, ideas, solutions?
> > >
> > >
> > >I have one solution in mind but it is not very elegant. I will share
> > >this next week when you have had time to think about the problem.
> > >
> > >
> > >------------
> > >
> > >A distribute-list applied to R3, an ABR, will of course not work. (When
> > >the 10.1 route reaches R3 it is in an LSA. If we apply the distribute-
> > >list x in, it will only block the route going into R3's routing table,
> > >it will not prevent the LSA from being sent on to R4. We are not
> > >permitted to change the other routers in Area 0 so we can not use the
> > >conventional approach of applying the distribute-list x in to each of
> > >the routers in Area 0.
> > >
> > >If we apply a distribute-list x out to the ABR it will again have no
> > >impact on the LSA advertising the 10.1 route into Area 0.)
> > >
> > >==========================
> > >
> > >May enlightenment be yours.
> > >
> > >Peter
> > >
> > >--
> > >Peter Whittle
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