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Re: Advertising Routes learnt from PE to PE

  • From: Aamer Akhter <aakhter@cisco.com>
  • Date: Wed, 14 May 2003 11:16:20 -0400
  • CC: <mpls@uu.net>
  • Resent-Date: Wed, 14 May 2003 12:32:07 -0400
  • To: "Sugar, Sylvia" <truesylvia@yahoo.co.uk>, <mpls-ops@mplsrc.com>
  • User-Agent: Microsoft-Entourage/10.1.1.2418

On 5/14/03 10:06 AM, "Sugar, Sylvia" <truesylvia@yahoo.co.uk> wrote:

> Hi,
> WIll a PE router ever advertise a route it learns from another PE router to
> some other PE router.
> I dont think it will ever do that as all the PE routers are IBGP peers and
> would generally be in
> full mesh. 

You're correct. The exception would a route-reflector / confederation. But
as you know by default, these bgp nodes don't change the next-hop.

> 
> Is there any case when this might happen .. i.e. a PE router advertises a
> Route learnt from one PE
> to another PE. How can one do that .. because IMHO the label that will be
> advertised by the former
> PE router will be for the PE router to which he sends the UPDATE. How can this
> PE router advertise
> another PE router the same label?
> 
> Moreover, if for some reason he has to .. does he assign a new label and then
> advertise?

A RR will allocate a label (locally) if the next-hop changes. Of course this
doens't mean much unless the next-hop is the RR itself. ;-)

> 
> ANy comments on this would be very helpful!
> 
> Silviya Sugar
> 
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-- 
Aamer Akhter / aa@cisco.com
NSITE - cisco Systems


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