Re: MPLS forwarding in partial mesh frame-relay networks

Rich,

I am not sure why there is a targeted session there. I don't see how
targeted would fix it. Because (using Steve's example), if R2 had an LDP
session to R3 and then could use the label that R3 advertised, it would be a
pop-label...not the label advertised by R1. Therefore, the inner (VPN) label
still gets exposed to R1 as the packet gets forwarded. Does that explain it?

On Fri, Jan 22, 2010 at 2:44 PM, Rich Collins <nilsi2002_at_gmail.com> wrote:

> Hi Bryan,
>
> Thanks for that clarification.
>
> I was wondering if or how the "targeted LDP sessions (between B&C)"
> come into play in this scenario?
>
> -Rich
>
>
>
> > On Sat, Jan 23, 2010 at 12:08 AM, Bryan Bartik <bbartik_at_ipexpert.com>
> wrote:
> >>
> >> Cool. In case you are wondering how the router might know the next-hop
> >> address belongs to the downstream LSR...it is contained in an address
> >> mapping message. The LSR basically sends all its interfaces addresses,
> so
> >> the peer can look them up and tell if it can install the label or not.
> If
> >> you do a "show mpls ldp neighor" at the bottom you will see a section
> called
> >> "Addresses bound to peer LDP Ident:"
> >>
> >> On Fri, Jan 22, 2010 at 11:31 AM, Divin Mathew John <
> divinjohn_at_gmail.com>
> >> wrote:
> >>>
> >>> Oh.! Thats was something !
> >>>
> >>> On Fri, Jan 22, 2010 at 11:56 PM, Steve Shaw <shaw38_at_gmail.com> wrote:
> >>>>
> >>>> Bryan,
> >>>>
> >>>> Thanks! That's the rule I was looking for.
> >>>>
> >>>> Steve
> >>>>
> >>>> On Fri, Jan 22, 2010 at 1:03 PM, Bryan Bartik <bbartik_at_ipexpert.com>
> >>>> wrote:
> >>>>
> >>>> > Rich,
> >>>> >
> >>>> > An LSR will only install a label for a prefix if the next-hop for
> that
> >>>> > prefix is an address that belongs to the router from which it
> learned
> >>>> > the
> >>>> > label. So if Router B's next-hop for Router C is Router C's address,
> >>>> > it will
> >>>> > not install the label because the label was learned from Router A.
> >>>> >
> >>>> > What you can do to fix this is install a static route on router B
> for
> >>>> > C's
> >>>> > address that points to A as the next-hop. Now the label learned from
> A
> >>>> > will
> >>>> > be installed.
> >>>> >
>

-- 
Bryan Bartik
CCIE #23707 (R&S, SP), CCNP
Sr. Support Engineer - IPexpert, Inc.
URL: http://www.IPexpert.com
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