From: Carlos G Mendioroz (tron@xxxxxxxxxxx)
Date: Fri Jun 28 2002 - 18:09:37 GMT-3
Peter,
run 2 OSPF processes at R3, and redistribute between them...
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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