Re: Just shy of OT MPLS Question

I think I answered the question in my previous mail :-)

You CAN use BGP to get rid of an IGP, but you CAN'T use LDP then, LDP uses an
IGP protocol to allocate labels. If you want to allocate labels for BGP
prefixes, you should use BGP as label distribution as well (neighbor
send-label command).

On the other hand, I would never implement this. An IGP with LDP is far more
easier to setup and maintain than using BGP for this purpose.

--
Regards,
Rick Mur
CCIE2 #21946 (R&S / Service Provider)
Sr. Support Engineer  IPexpert, Inc.
URL: http://www.IPexpert.com
On 23 dec 2009, at 12:43, <Keegan.Holley_at_sungard.com> wrote:
> That's interesting.  I think that was my original question whether you could
build your base routing table using bgp and have LDP/RSVP base it's label
assignments on it.  I knew you could do it with statics (routes not labels
sorry..)  So just so I'm sure I understand you're saying that there's no way
to replace your IGP with bgp even if the next-hop and other issues are taken
care of?  I was just curious since I've seen some of the smaller carriers
where every router is a PE router so you cannot get away from doing BGP in the
core.  I was just curious if there was a way to keep from doing the IGP in the
core and maybe save some resources that way even at the expense of TE.
>
>
> From:	Rick Mur <rmur_at_ipexpert.com>
> To:	<Keegan.Holley_at_sungard.com> <Keegan.Holley_at_sungard.com>
> Cc:	ALL From_NJ <all.from.nj_at_gmail.com>, Cisco certification
<ccielab_at_groupstudy.com>, nobody_at_groupstudy.com, Scott Morris
<smorris_at_ine.com>, JR Garcia <ttuner_at_gmail.com>
> Date:	12/23/2009 03:00 AM
> Subject: 	Re: Just shy of OT MPLS Question
>
>
>
>
> The IGP label is usually the 'outer' label (unless another label get's
attached in a CsC environment). Inner label is the VPN label, Outer label is
the IGP label.
>
> A flat MPLS network with statics? I would never ever build a network with
static label assignments :-) (doesn't even work on Cisco, it does on Juniper)
>
> You can't use BGP and LDP to assign labels. If you want BGP prefixes to get
a label allocated, you do this within BGP and then BGP advertises and assigns
labels for those prefixes. This will definitely work. So NO LDP then :-)
>
> --
> Regards,
>
> Rick Mur
> CCIE2 #21946 (R&S / Service Provider)
> Sr. Support Engineer  IPexpert, Inc.
> URL: http://www.IPexpert.com
>
> On 23 dec 2009, at 03:52, <Keegan.Holley_at_sungard.com>
<Keegan.Holley_at_sungard.com> wrote:
>
>
> <nobody_at_groupstudy.com> wrote on 12/22/2009 02:36:40 AM:
>
> > I'm also a bit confused with the term MPLS Tunnels. Do you mean a
> > normal MPLS VPN or a TE Tunnel, since both require totally different
things.
> >
> Neither, I'm not that familiar with the term.  I always took tunnel to mean
anything encapsulated in something else and thus interchangeable with LSP.  In
other words I meant LSP's.
>
> > For IBGP it's not really recommended and same as Bryan said, I never
> > tested this. It does is an implementation for Inter-AS
> > configurations to use the BGP send-label command to advertise
> > prefixes and labels in BGP, which works :-)
> >
>
> Are these inner or outer labels? Inner with one outer to keep you from
having to run LDP with a foreign router? I would assume they are the inner
labels and then your RSVP/LDP protocol would take care of the outer labels
used to reach the next AS's router.
>
> > For TE tunnels, you cannot allocate labels through BGP, but solely
> > through RSVP and a link-state protocol. This is because of he
> > dynamic behavior and the SPF protocol that TE uses to calculate
> > paths throughout the network. A distance vector protocol like BGP
> > would not work as within a link-state you have the full topology of
> > the network available to calculate your path on (within an area of
course).
>
> Throw TE (and usefullness with it...) out the window for a minute.  For
example you can create a flat MPLS network using static routes.
>
> >
> > So for MPLS VPN's this should work, advertise the PE loopbacks in
> > IPv4 BGP and advertise VPN labels in VPNv4 BGP. You should run BGP
> > on the P of course then. Cool thing to lab it up :-)
>
>
> Could you use BGP as the only protocol and just enable LDP on each interface
to do the switching?  Assuming next hop reachability was taken care of
(without static routes).  Don't have any SP stuff setup right now or I'd try
it out myself.
>
> >
> >
> > --
> > Regards,
> >
> > Rick Mur
> > CCIE2 #21946 (R&S / Service Provider)
> > Sr. Support Engineer  IPexpert, Inc.
> > URL: http://www.IPexpert.com
> >
> > On 22 dec 2009, at 06:29, Scott Morris wrote:
> >
> > > Yup, you can.
> > >
> > >
> > >
> > >
> > > *Scott Morris*, CCIE/x4/ (R&S/ISP-Dial/Security/Service Provider)
#4713,
> > >
> > > JNCIE-M #153, JNCIS-ER, CISSP, et al.
> > >
> > > JNCI-M, JNCI-ER
> > >
> > > evil_at_ine.com
> > >
> > >
> > > Internetwork Expert, Inc.
> > >
> > > http://www.InternetworkExpert.com
> > >
> > > Toll Free: 877-224-8987
> > >
> > > Outside US: 775-826-4344
> > >
> > >
> > > Knowledge is power.
> > >
> > > Power corrupts.
> > >
> > > Study hard and be Eeeeviiiil......
> > >
> > >
> > >
> > > JR Garcia wrote:
> > >> pretty sure you can exchange labels via ibgp using the "send-label"
> > >> command. Eg: neighbor 1.1.1.1 send-label
> > >
> > >
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