Re: BGP "Allowas-in" -- scenarios to use this?

Great example and explanation Marko.

As Marko says, it is very common w/ MPLS, as some SPs will assign each
customer only one private AS for all their sites, nd in some cases,
regardless of the number of sites.

On Tue, Aug 18, 2009 at 10:49 AM, Marko Milivojevic <markom_at_markom.info>wrote:

> On Tue, Aug 18, 2009 at 14:34, Adrian<ccie2323_at_gmail.com> wrote:
> > dun think it will ever happen. unless for private AS. B Have 2 remote
> sites
> > that is having the same as that transit a different AS in the middle.
> >
> > AS100-AS200-AS100
>
> This is actually somewhat common in MPLS VPN deployment scenarios.
> Imagine Enterprise (say with AS65000) that has MPLS provider with AS
> 65100. They have several sites and run BGP:
>
> (site1: AS65000) --- (MPLS: AS65100) --- (site2: AS65000)
> (site3: AS65000) ----^
>
> As you can see, all customer sites are in AS65000. When update from
> site1 arrives to either site2 or site3, AS_PATH will look like "65001
> 65000". Site2 will, of course, reject this as looped.
>
> One of the solutions how to overcome this situation is to use "bgp
> allowas-in". There are others, but they require configuration by
> service provider - who may be unwilling to change their configurations
> and let customers deal with their issues, without getting too
> involved.
>
> --
> Marko
> CCIE #18427 (SP)
> My network blog: http://cisco.markom.info/
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
>
>
>
>
>
>

-- 
Andrew Lee Lissitz
all.from.nj_at_gmail.com
Blogs and organic groups at http://www.ccie.net