[c-nsp] MPLS down to the CPE

Phil Bedard philxor at gmail.com
Wed Jul 10 21:48:24 EDT 2013

On 7/10/13 4:16 AM, "Adam Vitkovsky" <adam.vitkovsky at swan.sk> wrote:

>> the different network islands are tied together using CsC over
>> a common MPLS core.
>You got me scared for a moment CsC would mean to run a separate
>OSPF/LDP/BGP-ASN for each area and doing MP-eBGP between ASBRs within each
>area(OptB) or between RRs in each area(optC) with core area/AS acting as a
>labeled relay for ASBRs loopback addresses, though I believe by common
>core you mean a single AS right please?

The islands are actually all in the same ASN, the common core is not the
same ASN.  Could have been the same ASN, more political reasons for it not
being the same than technical.  In the end it looks like Option C, the CsC
L3VPN only carries loopbacks and aggregate IP prefixes.   The common core
is RSVP-TE based, if I had my preference today I would build TE tunnels
across it between the islands and then use RFC3107 as a way to tie it all
together end to end.  Years ago when we first built it some of the feature
support wasn't there to do that.

>> At the ABR all of the L2VPN services are "stitched" since you are
>> entering a different RSVP-TE/MPLS domain, the L3VPN
>> configuration exists on these nodes with the access nodes using
>> L2 pseudowires into virtual L3 interfaces.
>I see, right that's a clever way to save some money by pushing the L3VPN
>stuff to only a few powerful boxes with high-queue line cards and L3VPN
>licenses. Though the PWHE -a setup where you can actually terminate the PW
>into L3 interface on the same box was introduced to Cisco boxes only
>recently so prior to that you'd have to have a separate box bridging the
>to sub-int/serv-inst on a QinQ trunk where the L3VPN box would be
>I'm still confused about the TE part.
>So I believe you are pushing PW directly into TE tunnels what gives you
>ability to balance the PWs around the ring as well as to use a backup
>via the opposite leg of the circuit. So the TE tunnels are actually
>terminated on the PWHE nodes right? Or do they actually continue into the
>backbone area please?

The tunnels from the access boxes terminate on the PWHE nodes, they do not
extend beyond that boundary.  There is another set of tunnels which
connect the PWHE nodes together.  This isn't a one-off deployment or
anything, there are other folks out there with basically the same type of



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