[c-nsp] iBGP full-mesh requirement for MPLS VPN CE

[Bruce Pinsky]

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Ravi Vaidyanathan wrote:
> Hi, 
> 
> I have two CE routers connecting to a MPLS VPN at 2 distinct geographical
> locations using the same AS number. Does the iBGP full-mesh requirement hold
> for such a scenario (i.e. do the two CE routers need to run iBGP with each
> other)? If so, can someone explain what the utility of running iBGP in such
> a scenario is? 

If you are connecting to a provider's MPLS/VPN, you would be using eBGP
normally.  The routes you exchange with the provider should be carried
through the provider's MP-BGP infrastructure and handed off to any/all of
your other locations again via eBGP.  Using the same ASN at each location
should be fine if your provider allows for it in their MPLS/VPN service model.

The only time iBGP between your CE sites is normally used is when you have
your own MPLS infrastructure and need to have a Carrier Supporting Carrier
(CsC) relationship by exchanging labels with your provider via BGP+Label or
LDP.  In that case, you are passing only the route to each of those CE's
loopback (or physical interface) address that is used for the iBGP peering
through the provider cloud and you manage all the sites' routes in your own
BGP control plane.

- --
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bep

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