All interfaces on a router running OSPF must belong to the same area.
All interfaces on a router running OSPF must belong to the same area.
All interfaces on a router running OSPF do not have to belong to the same area. OSPF routers can have interfaces in different areas. This capability is part of the OSPF's design to support a hierarchical network structure with multiple areas to optimize traffic and reduce routing table size.
One router can have interfaces in different areas