All of you are might be aware of super backbone concept in mpls. No issue if you don't know I will let you in couple of words. As per super backbone concept service provider network will work as area 0 for customer links. It means for every vpn which is using OSPF as PE-CE routing protocol no need to configure area 0. Without introducing area 0 all links of the vpn can communicate with each other. This is all about super backbone concept. But what happens if customer will use area 0 in his network. So simply ask customer to extend area 0 till your PE but as per my experience none of the customer will do that. Consequently an immense problem can occur if customer will not extend the area 0 till PE. See in Figure 1 which clearly depicts that customer is having their area 0 but PE2 – CE2 connectivity is on OSPF area 1. Now CPE routes cannot be forwarded across the MPLS cloud because CPE is getting two number of area 0; one from its own & another is from service provider.

Workaround

a)Ask your customer to extend the area 0 till you PE.