[c-nsp] BGP Route Nailing & Reoriginatin

[Shakeel Ahmad]

I just read somewhere we can use

set origin .... command in a route-map to alter the origin codes for
incoming routes

So if this works (which it should) you need to configure a route-map on R2
to mend the origin code for prefixes 1.1.1/24 & 2.2.2/4 and set it to
igp...(someone please correct me here if i am wrong)


thanks,
SA


On 12/5/06, Shakeel Ahmad <shakeelahmad at gmail.com> wrote:
>
> Umm i would do it like this  --- Two options (idealy i would go with
> second but not sure what your requirment is)
>
> * Concidering you want BGP still running between R1 & R2
>
> Use Conferdeation in between R1 & R2 with AS2 as Confederation Identifier
> so that AS3 only knows about AS2 (two private AS can be used on R1 & R2 to
> hide in AS2 identifer) .. Solves your issue !!!
>
> * Concidering we don't want (or should'ny) run BGP in between R1 & R2
>
> on R2/AS2 put static routes for 1.1.1.0/24 & 2.2.2.0/24 towards R1
> (There's no point of BGP running in between R1 & R2 in this case). Now in
> your BGP session at R2, advertise 1.1.1/24 & 2.2.2/24 via network
> statement. It'll solve the first issue.....and R3 will recieve 1.1.1/24 &
> 2.2.2/24 as originated by AS2 -
>
>
> now points come to stop flapping , simply (also a best practice for both
> above) put these static routes on R2/AS2
>
> ip route 1.1.1.0/24 Null 0 250
> ip route 2.2.2.0/24 Null 0 250
>
> Remmember metric should be as lowest as possible and the subnet thrown on
> Null 0 should be as aggregated as possible. This will eventaully stop your
> flaps and routes will never disappear from AS3 and will always point back to
> AS2.
>
>
> hope this helps....
>
> Shakeel Ahmad
>
>
>  On 12/5/06, Lawrence Wong <lawrencewong72 at yahoo.com> wrote:
> >
> > Dear gurus,
> >
> > I have an environment as follows:
> >
> >        (R1 / AS1) <-> (R2 / AS2) <-> (R3 / AS3)
> >
> >
> > R1 (router 1) has AS number 1 (AS 1) and advertises the routes
> > 1.1.1.0/24 and 2.2.2.0/24 to R2 which inturn advertises to R3. All
> > advertisement is done via eBGP.
> >
> > Is it possible to configure R2 such that the routes 1.1.1.0/24 and
> > 2.2.2.0/24 are advertised to R3 under AS2 instead of AS1? At the same
> > time, can R2 "nail" down the routes so that in the event the (physical &
> > BGP) link between R1 and R2 is down, the route continues to be advertised to
> > R3 (and under AS2)?
> >
> > The objective is to "hide" AS1 and also to prevent BGP dampening at R3
> > caused by flapping link between R1 & R2.
> >
> >
> > TIA!
> >
> >
> >
> >
> >
> >
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