You cannot configure multiple vrfs on an ospf instance you need a separate instance for each VRF.
If it was possible to configure multiple VRF's on an ospf instance, using separate instances would not be wrong.
P2#sh run | section router
P2#
P2#
P2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
P2(config)#router ospf 10 vrf Site-A
P2(config-router)#
*Feb 24 07:16:28.883: %OSPF-4-NORTRID: OSPF process 10 failed to allocate unique router-id and cannot start
P2(config-router)#router-id 10.10.10.10
P2(config-router)#exit
P2(config)#
P2(config)#router ospf 10 vrf SharedSites
%VRF specified does not match existing router
P2(config)#
P2(config)#
P2(config)#
P2(config)#router ospf 20 vrf SharedSites
P2(config-router)#
*Feb 24 07:17:31.696: %OSPF-4-NORTRID: OSPF process 20 failed to allocate unique router-id and cannot start
P2(config-router)#router-id 20.20.20.20
P2(config-router)#exit
P2(config)#
P2(config)#
If it was possible to configure multiple VRF's on an ospf instance, using separate instances would not be wrong.
P2#sh run | section router
P2#
P2#
P2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
P2(config)#router ospf 10 vrf Site-A
P2(config-router)#
*Feb 24 07:16:28.883: %OSPF-4-NORTRID: OSPF process 10 failed to allocate unique router-id and cannot start
P2(config-router)#router-id 10.10.10.10
P2(config-router)#exit
P2(config)#
P2(config)#router ospf 10 vrf SharedSites
%VRF specified does not match existing router
P2(config)#
P2(config)#
P2(config)#
P2(config)#router ospf 20 vrf SharedSites
P2(config-router)#
*Feb 24 07:17:31.696: %OSPF-4-NORTRID: OSPF process 20 failed to allocate unique router-id and cannot start
P2(config-router)#router-id 20.20.20.20
P2(config-router)#exit
P2(config)#
P2(config)#