From: Godswill Oletu (oletu@inbox.lv)
Date: Sun Apr 22 2007 - 21:37:53 ART
Alternatively, you can conditionally filter the routes on R2 & R3 as they
are receive from R1 and prevent the non-preferred route from entering the
routing table.
Godswill Oletu
CCIE #16464
----- Original Message -----
From: "Godswill Oletu" <oletu@inbox.lv>
To: "Suplepo" <suplepo@yahoo.com>; <ccielab@groupstudy.com>
Sent: Sunday, April 22, 2007 7:51 PM
Subject: Re: BGP path manipulation
> Hi Suplepo,
>
> Think of route advertisement and traffic flow as opposite in direction.
From
> your scenario, R1 will originate and advertise both routes into BGP and to
> eg R2 & R3.
>
> If the routes are not manipulated traffic from devices beyond R2 & R3 will
> choose beween R2 & R3 to reach networks 1.1.1.1/32 & 2.2.2.2/32 on R1.
>
> My guess is, the task is asking you to eliminate the choice inherent in
the
> above scenario. eg if you configure R2 to disallow it from advertising one
> of the routes to devices beyond it; traffic from devices beyond R2 will
have
> to source that network from other means e.g from R3.
>
> Likewise, filter the other route from R3 advertisements and you will be
> closer to fulfilling the requirements for the task.
>
> HTH
>
> Godswill Oletu
> CCIE #16464
>
>
> ----- Original Message -----
> From: "Suplepo" <suplepo@yahoo.com>
> To: <ccielab@groupstudy.com>
> Sent: Sunday, April 22, 2007 12:21 PM
> Subject: BGP path manipulation
>
>
> > I'm working through a sample lab and have hit a snag.
> >
> > R1 Is advertising networks 1.1.1.1/32 and 2.2.2.2/32
> > into BGP. Instructions state
> >
> > 1) Configure R3 so that it's the preferred path for
> > traffic network 1.1.1.1/32
> >
> > 2) Configure R2 so that it's the preferred path for
> > traffic to network 2.2.2.2/32
> >
> > I can easily do this with AS-path prepending or MED,
> > but since both of these must be configured on the
> > non-desireable path I'm stuck. Is there anything I can
> > do on the desired inbound path (R3 for 1.1.1.1) to
> > ensure it's the best path. Since R1 is advertising the
> > routes to both R2 & R3 conditional advertisement from
> > R3 and R2 will not work.
> >
> > This all has me thinking I looking at a mistake in the
> > question, but thought I'd bounce it off the collective
> > to make sure there's not another option.
> >
> > Topology below,
> > iBGP peerings R1<->R2, R1<->R3, R3<->R2
> > eBGP peerings R3<->R4, R2<->R4
> >
> > |
> > AS1 | AS2
> > |
> > R3--------eBGP-----------R4
> > |\ |
> > | \ |
> > | R1 |
> > | / |
> > | / |
> > R2---------eBGP----------|
> >
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