From: Larson, Chris (CLarson@usaid.gov)
Date: Mon Sep 23 2002 - 10:08:57 GMT-3
I would agree that prepending AS would work. You can also use communities to
affect this, at least with those ISP's that allow it (SPRINT for one, I
know). I think you could also adjust the MED. This may not be valid if you
are using a different ISP at each link.... except for AS-paths. Those should
always work.
> -----Original Message-----
> From: Tim O'Brien [SMTP:tobrien@cinci.rr.com]
> Sent: Monday, September 23, 2002 8:21 AM
> To: Gibbs, John; 'John Mistichelli'; Asim Khan; ccielab@groupstudy.com
> Subject: RE: Basic BGP decision process
>
> John,
>
> I disagree.
>
> Why couldn't you prepend your own AS several times to the routes within
> your
> control that you want to look less attractive for whatever link you don't
> want them to take and then advertise that back out to your ISP. That
> should
> make the other link look more attractive to incoming traffic having less
> hops to your AS.
>
> Tim
> CCIE 9015, CSS1
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Gibbs, John
> Sent: Monday, September 23, 2002 4:36 AM
> To: 'John Mistichelli'; Asim Khan; ccielab@groupstudy.com
> Subject: RE: Basic BGP decision process
>
>
> I agree with John on this one - there is nothing you can do to influence
> which inbound path a packet will take. I say try the cash option!
>
> Regards
> John Gibbs CCNP CNE ACA
> Senior Network Consultant
> Engineering Services
> Service Delivery
> Internet Services
>
> Cable & Wireless
> Delivering the Internet promise
> www.cw.com <http://www.cw.com>
>
> email: john.gibbs@cw.com
> Tel: 44 (0)1793 362334
> Fax: 44 (0)1793 362062
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> SN5
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>
>
>
> -----Original Message-----
> From: John Mistichelli [mailto:jmistichelli@yahoo.com]
> Sent: 22 September 2002 21:16
> To: Asim Khan; ccielab@groupstudy.com
> Subject: Re: Basic BGP decision process
>
>
> The way I see it--Outbound policy is completely within
> your control. Inbound policy unfortuantely is not. The
> best you can hope for is to provide a "hint" to the
> neighboring AS. If that AS decides to take the hint
> then you are fortunate.
>
> If that administrator will not cooperate you can
> always try cash! ;)
>
> Cheers,
> John
> 7536
> ______________________________________________________
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>
> --- Asim Khan <asimmegawatt@yahoo.com> wrote:
> > Hi all,
> >
> > Suppose we have 4 routers Ra, Rb, Rc and Rd. Ra is
> > in
> > AS10 and Rb, Rc and Rd are in AS20 as shown below:
> >
> > AS10
> > | loopback 1.1.1.1/32
> > |
> > Ra
> > / \
> > Link 1 / \Link 2
> > -------------------------------
> > / \
> > Rc Rb
> > AS20 \ /
> > \ /
> > \ /
> > \ /
> > Rd
> > Now suppose the Administrator of AS20 wants all
> > outgoing traffic to take Link 2, so he set the local
> > preferance on Rb for incoming routes (1.1.1.1) from
> > Ra
> > as 200 and on Rc as 100(default). Rb,Rc and Rd are
> > in
> > full meshed. It means to reach 1.1.1.1 router Rd
> > will
> > take the path of Link 2. Now the administrator of
> > AS10
> > wants to influence the incoming traffic from AS20
> > and
> > force them to use Link 1. So he set the MED 5 for
> > all
> > the outgoing routes via Link 1 and the MED 10 for
> > all
> > the outgoing routes via Link 2.
> >
> > I know in BGP decision process local preference
> > comes
> > first then MED and in general BGP policies establish
> > after mutual consultation of both the Administrator.
> >
> >
> > But in this particular case, when both the
> > administrator are in complete disagreement, which
> > link
> > will be used for traffic going from AS20 to AS10.
> >
> > If Link 2 is used then is there any way for
> > Administrator of AS10 to force AS20 to use Link 1.
> >
> > Regards.
> >
> > Asim Khan
> >
> >
> >
> > __________________________________________________
> > Do you Yahoo!?
> > New DSL Internet Access from SBC & Yahoo!
> > http://sbc.yahoo.com
>
>
> __________________________________________________
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