This read-write object stores the subnet mask paired with wvLinkIPAddress, expressed as an IP-formatted value with the network bits set to 1 and the host bits set to 0. It tells the terminal how much of the link IP address space is treated as the local network versus host addressing, which determines whether traffic to a given peer is routed or considered directly reachable across the link. For instance, setting this to 255.255.255.252 alongside a /30-sized wvLinkIPAddress assignment restricts the link subnet to just the two terminal endpoints.