OSPF as CE-PE question

Hi Experts,
I have a question in OSPF as CE-PE.

I understood that, if the CE to PE is non-backbone area, then we need to
extend the backbone till the PE, so we can use either virtual-link or GRE
tunnel.

But, my question is, if both CE1-PE1 and CE2-PE2 are non-backbone areas and
both are in different areas, do we need to extend the backbone on the both
the CEs, one one-side is enough?

Topo would look like this:

  PE1--------------------PE2
   | |
   | |
   | |
Area-2 Area-3
   | |
   | |
   | |
  CE1-----Area-0----CE2 or may be some others routers in bewtween CE1 and
CE2, that are part of Area-0.

Thanks,
Usha

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Received on Sat Dec 04 2010 - 13:34:24 ART