From: Andy (and123and@googlemail.com)
Date: Thu Mar 13 2008 - 08:54:07 ARST
HI
by redistributing the routes in you are effectively setting them to "?", and
in this way you are influencing how R2 advertises the routes.
hth
On 13/03/2008, YourPal <dearprudence28@gmail.com> wrote:
>
> Hi All,
>
> Those 3 prefixes are loopback addresses of the respective router. They are
> not advertised in IGP.
>
> An earlier task asks to advertise those loopbacks into BGP with no
> restriction. Then comes this task that restricts configuration on R1 only.
> Is it possible at all? I still think that we need to configure something
> on
> R2 (whether setting MED, community, origin code, etc) in order to satisfy
> this task, if that's allowed at all.
>
>
> Thank you.
>
> BR,
> Emil
>
>
> On 3/13/08, Shine Joseph <shinepjoseph@iprimus.com.au> wrote:
> >
> > Emil,
> >
> > The fact that origin code is ahead of MED in best path calculation, you
> > can
> > change the origin code to accomplish this task.
> >
> > If there is no restriction in how you advertise the networks in AS123, I
> > can
> > think of advertising the network with origin code of igp to R4 from R1.
> If
> > you are restricted with no-redistribution, then apply a route-map in the
> > network statement to change the origin code to incomplete.
> >
> > I have labbed up your scenario and it works.
> >
> > HTH,
> > Shine
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > YourPal
> > Sent: Thursday, 13 March 2008 5:19 PM
> > To: Cisco certification
> > Subject: Question on Influencing BGP Inbound Path Selection
> >
> > Hi Group,
> >
> > I came across the following BGP scenario:
> >
> > R1, R2, and R3 are in AS 123. They are fully-meshed. R4 is in AS 456. R4
> > peers with R1 and R2.
> >
> > R1 advertises 172.16.1.1/32 into BGP.
> > R2 advertises 172.16.2.2/32 into BGP.
> > R3 advertises 172.16.3.3/32 into BGP.
> >
> > Configure R1 so that R4 prefers R1 to reach 172.16.1.1/32 and
> > 172.16.3.3/32.
> > Route filtering and AS path manipulation are prohibited.
> >
> > The way I see it, I'm left with the option of configuring MED. However
> > since
> > the task restricts the config to be done on only R1, AFAIK there's no
> way
> > to
> > influence MED because both R1 and R2 will advertise the prefixes to R4
> > with
> > MED=0 (unless I'm allowed to configure a higher MED value on R2).
> >
> > Can't think of a solution. I may be missing something. Appreciate any
> > help.
> >
> >
> > Thank you.
> >
> > BR,
> > Emil
> >
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