RE: BGP path selection process, confederation peer's AS numbers

From: Jason Guy \(jguy\) (jguy@cisco.com)
Date: Tue Jul 10 2007 - 15:47:42 ART


Yeah, I misunderstood what you were asking...

> -----Original Message-----
> From: John Gibson [mailto:johngibson1541@yahoo.com]
> Sent: Tuesday, July 10, 2007 2:41 PM
> To: Jason Guy (jguy)
> Cc: ccielab@groupstudy.com
> Subject: RE: BGP path selection process, confederation peer's AS
numbers
> doesn't count toward AS path lengh right?
>
> We are not talking about the same thing.
>
> Yes, (65502) is stripped when going out of the
> big AS (the typically registered).
>
> But within the big AS, when a different confed
> receives "(65502)" , this "(65502)" does not
> count toward "AS path length". My key emphasis is
> "length" here.
>
> My experiment has Path of "(65502) 200 i" and
> "100 i" of 2 routes arriving at the router.
> And I use always compare med.
>
> When I change med (set metric) from outside the big
> AS, it effects path selection. MED is lower ranked
> than AS path length. This means "(65502) 200 i" and
> "100 i" are considered of the same "As path length".
>
> Mike Kraus says I am correct.
>
>
> John
>
>
> --- "Jason Guy (jguy)" <jguy@cisco.com> wrote:
>
> > John,
> >
> > The AS-Path counts within the confederation. As
> > soon as the prefix is
> > advertised outside (to the real world) the
> > confederation AS-path is
> > stripped, and the global AS is prepended. Within
> > the confederation,
> > most of the same eBGP rules apply.
> >
> > The MED value can be set regardless of where the
> > prefix is advertised
> > (confed peer or other peer).
> >
> > Jason
> >
> >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com
> > [mailto:nobody@groupstudy.com] On Behalf
> > Of
> > > johngibson1541@yahoo.com
> > > Sent: Tuesday, July 10, 2007 2:18 PM
> > > To: ccielab@groupstudy.com
> > > Subject: BGP path selection process, confederation
> > peer's AS numbers
> > > doesn't count toward AS path lengh right?
> > >
> > > I have tried to use MED to influence 2 routes
> > >
> > > one with "(65502)" confederation peer AS
> > >
> > > another without the confederation peer AS
> > >
> > > MED takes effect.
> > >
> > >
> > > John
> > >
> > >
> >
>



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