[c-nsp] Network Design - OSPF Convergence Issue

[Shakeel Ahmad]

Guys,

we came across a live scenario here and i am not a big OSPF guru...please
guide me here

                +               ++ HQ ++
                |
                |       --         P1
                |       |       / / | \ \
                |       OSPF
                |       |       \ \ | / /
                |       --      1 2 3 4 5
                |
                +                ++Core++


Client is running simple GRE tunnels via 5 different providers (1,2,3,4,5)
to their headquarter's ISP (P1)...   All providers are connected on
different boundry routers  and HQ on a single router..

Now Loopback IP's are advertised via OSPF (single area) for all boundry
routers of client and HQ....Issue currently faced is: loopback IP's are
learnt from all GRE tunnels...while changing Costs on different GRE tunnels
doesn't change the traffic path and CORE learns the path from (low cost GRE
tunnel boundry router)..while BGP ssession is being used for distributing
....

The basic need is to converge the network in between boundry routers ON
DEMAND and sometimes on incident based events.

Can someone share..what would be the best design...covering ON DEMAND path
selection via OSPF in this design.

(i guess i confused many things..let me have your questions)

Regards,
Shakeel