Answer: Subnet mask
Explanation:
Subnet mask is the type of parameter that should be match in order to form the adjacency for running the OSPFv2. The subnet mask is mainly used to identifying the address of network in the system.
The OSPF enable the router that must form an adjacency with the neighbors before sharing any type of data.
It mainly determine the neighbors links in the OSPF. The OSPFv2 router send the special type of message which is known as hello packet in the network.
