Can routers with matching OSPF router IDs become neighbors?

In OSPF (Open Shortest Path First), each router must have a unique router ID within the same OSPF domain. This router ID is a 32-bit value that uniquely identifies each OSPF router and is typically derived from the router’s highest IP address on an active interface or explicitly configured. If two routers were to have matching router IDs, they would not be able to establish a neighbor relationship, as OSPF relies on unique identifiers to manage neighbor relationships and maintain accurate link-state databases.

When routers attempt to form an OSPF neighbor relationship, they exchange Hello packets that contain their router IDs. If the router IDs are the same, confusion arises because OSPF cannot differentiate between the two routers. Consequently, the routers will not treat each other as distinct neighbors, thereby preventing any adjacency from being formed.

This restriction ensures efficient routing and prevents issues that could arise from multiple routers being indistinguishably represented in the OSPF network topology. Without unique identifiers, the fundamental operations of OSPF, such as topology convergence and route calculation, would be disrupted.