Re: BGP SoO

Antonio,

Generally speaking if you're on the SP side you use as-override and when you
work for the customer you can use the allowas-in to accept a route even if
you see your own AS number on the list of traversed AS's. Many limitations
affect these decisions though.

At the end of the day, my recommendation, if you're running for the R&S
track is, please don't overkill MPLS. You're not expected to deal with super
tricky situations. Believe it or not I've seen some R&S students in my
classes crying out because wow MDT in inter-as vpn option 2 does not work!!!
don't waste your time on this kind of stuff and focus on LDP, simple MPLS,
RD, RT and VRF lite. You will make it happen.

HTH
Kambiz Agahian

CCIE Instructor/Consultant
CCIE# 25341, CCSI# 33326, MCSE, MCSA

On Thu, Jul 15, 2010 at 11:54 AM, Antonio Saez <
antonio.saez.jimenez_at_gmail.com> wrote:

> Ok, I understand it now, using SoO together as-override. That is a very
> clear example/picture.
>
> Thanks both for your help,
>
> One another question,.. as-override works in the incoming direction, isn't?
>
> Regards
>
>
>
> -----Mensaje original-----
> De: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] En nombre de
> Kambiz
> Agahian
> Enviado el: jueves, 15 de julio de 2010 19:17
> Para: 4g1vn; ccielab_at_groupstudy.com
> Asunto: Re: BGP SoO
>
> Well, it depends who you are :) but yes that's pretty much it.
>
> Please see this:
>
> http://fengnet.com/book/MPLS%20Configuration%20on%20Cisco%20IOS%20Software/i
> mages/1587051990/graphics/14fig56_alt.gif<http://fengnet.com/book/MPLS%20Configuration%20on%20Cisco%20IOS%20Software/i%0Amages/1587051990/graphics/14fig56_alt.gif>
>
> But still the critical point is that you clearly understand the difference
> between the allowas-in and as-override commands when it comes to designing
> a
> discontinuous BGP network. It's the difference between you can, you want
> and
> you should :) - Being the SP or the customer brings new challenges to this
> picture but in order to pass the R&S track don't worry about them.
>
>
> HTH
> Kambiz Agahian
>
> CCIE Instructor/Consultant
> CCIE# 25341, CCSI# 33326, MCSE, MCSA
>
>
>
> On Thu, Jul 15, 2010 at 10:09 AM, 4g1vn <shaun.gomez_at_gmail.com> wrote:
>
> > Great point Kambiz! So, if a customer is using the same AS number at each
> > location and you don't want to break the "normal" BGP loop prevention
> > mechanism using override or allowas-in. Use SoO! :)
> >
> >
> > On Thu, Jul 15, 2010 at 1:02 PM, Kambiz Agahian
> <aussiecert_at_gmail.com>wrote:
> >
> >> Antonio,
> >>
> >> Let's see the issue from this point of view; what if you have 10 BGP
> sites
> >> with the same AS number connected back to a provider? (like a Uni with a
> >> public AS number and 10 campuses connected to AT&T) what would you do to
> >> get
> >> things done in terms of normal updates? allowas-in or as-override
> >> solutions
> >> right? did you notice that you almost killed the native BGP loop
> >> prevention
> >> mechanism ? :)
> >>
> >> HTH
> >> Kambiz Agahian
> >>
> >> CCIE Instructor/Consultant
> >> CCIE# 25341, CCSI# 33326, MCSE, MCSA
> >>
> >>
> >> On Thu, Jul 15, 2010 at 8:25 AM, Antonio Saez <
> >> antonio.saez.jimenez_at_gmail.com> wrote:
> >>
> >> > Hi all,
> >> >
> >> > I don't understand the bgp SoO community. Imagine an scenario with two
> >> PE
> >> > routers speaking VPNv4 iBGP, 2 CE routers speaking iBGP and each PE
> >> router
> >> > speaking eBGP with on CE router. If one CE router send a prefix to the
> >> PE
> >> > router, and the Pe router to the other PE, then when the PE would send
> >> the
> >> > update to the CE, this CE router would discard the prefix because It
> >> would
> >> > see its AS in the AS Path.
> >> >
> >> > Please, tell me if I am wrong.
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > Blogs and organic groups at http://www.ccie.net
> >> >
> >> >
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> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
> > --
> > shaun
>
>
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Received on Thu Jul 15 2010 - 12:37:20 ART