Question about overlapping IP space and L3VPN central services

I'm just now getting around to really studying L3VPN. I'm playing around
with GNS3 while watching some training videos and my latest little lab
setup involves configuring basic central services. For the sake of
discussion, imagine three VRFs: A, B and C, as well as a new VRF called
SERVICES. I have customers in these VRFs spread out across the network, and
they do use overlapping IP space. When I configured this in my lab with one
customer, I found (remember, I'm new to this!) that I had to import the
customer routes into the new SERVICES VRF, which makes sense. Without those
routes in the VRF, the router can't forward packets to those destinations
even if the correct routes exist in other VRFs on that router.

But what happens when I import another customer into that table? Let's say
the VPN associated with VRF A is using 10/8 space, and so it the VPN
associated with VRF B. If I have already imported the routes for Customer A
into my Services VRF, how is this going to behave if I then import the
routes for Customer B using the same space? I realize that VPNv4 routes are
kept unique with the use of an RD. Does a PE router do something similar
when importing multiple sets of routes into a VRF? Does it retain the RD to
keep them unique somehow? If not, how do I handle having to import
overlapping prefixes to make central services work?

Thanks!
John

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Received on Sun Jul 29 2012 - 17:12:26 ART