Re: Just shy of OT MPLS Question

Keegan,

The main problems I find is that you get inconsistencies between
labels/next-hops. Consider this topology with no OSPF and IBGP+Send-label
instead:

PE1----P("RR")----PE2

In IBGP, next-hops do not change and the label gets reflected along with the
route. This means PE1 sees the loopback to PE2 with an imp-null label that
PE2 generated for itself. When PE1 sends packets toward PE2, there is no
"outer label" and the VPN label is exposed to the P router and breaks the
LSP.

There are several tweaks you can try but I never got it to work, although I
left some theories on the table :-)

On Mon, Dec 21, 2009 at 8:19 PM, ALL From_NJ <all.from.nj_at_gmail.com> wrote:

> lol ... you got me. Yes, the LDP protocol exchanges labels based on ... ?
>
> I was not technical enough in my quick answer. ;-)
>
> I am not sure why Cisco chose this ... (other than lower overhead on core /
> P routers)
>
> I am not very knowledgeable with Juniper, but I understand that Juni can do
> this with BGP? Probably someone smarter than me knows more about Juni ...
> I
> just have not ever studied them.
>
> What saith thee Juni guys? Super Scott has some Juni certs, maybe we can
> get the super Scott to respond.
>
> I am studying for a cvoice test! lol ... I think I am trying to fit too
> much into my little brain.
>
> Have a great night,
>
> Andrew
>
>
> On Mon, Dec 21, 2009 at 10:01 PM, <Keegan.Holley_at_sungard.com> wrote:
>
> >
> > Thanks for responding. Technically the outer labels come from LDP or
> RSVP.
> > They are then mapped to the route for the endpoints of the LSP/tunnel.
> I
> > was just wondering why this couldn't be built with BGP instead of an IGP.
> >
> > ALL From_NJ <all.from.nj_at_gmail.com> wrote on 12/21/2009 09:43:40 PM:
> >
> >
> > > Good evening Sir,
> > >
> > > I am pressed for time, so please forgive the quick and short
> > > response. Outer labels come from IGP, and not from BGP ... so no
> > > way to use BGP for this. HTH,
> > >
> > > Andrew Lee Lissitz
> > >
> >
> > > On Mon, Dec 21, 2009 at 9:07 PM, <Keegan.Holley_at_sungard.com> wrote:
> > > Does anyone know why you cannot use BGP routes to build MPLS tunnels.
> Is
> > > it the obvious (slow hello timers, possibly next hop ambiguity) or is
> > > there something inherent in the protocol suite (MPLS, RSVP, LDP) that
> > > makes it impossible.
> > > Not that I would ever want to... Just a little curious.
> > >
> > >
> > > Blogs and organic groups at http://www.ccie.net
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> > >
> > >
> > >
> > >
> >
> > >
> > >
> > >
> > > --
> > > Andrew Lee Lissitz
> > > all.from.nj_at_gmail.com
> >
>
>
>
> --
> Andrew Lee Lissitz
> all.from.nj_at_gmail.com
>
>
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-- 
Bryan Bartik
CCIE #23707 (R&S, SP), CCNP
Sr. Support Engineer - IPexpert, Inc.
URL: http://www.IPexpert.com
Blogs and organic groups at http://www.ccie.net