What Does Network Identity (Network ID) Mean?
A network ID, in the world of Transmission Control Protocol/Internet Protocol or TCP/IP, is the portion of the TCP/IP address which identifies the network for a given host, usually composed of three octets with dotted decimal representation.
Techopedia Explains Network Identity (Network ID)
In TCP/IP address syntax and protocol, an address is composed of four octets that are decimal-represented, instead of represented to end users in binary form. The fourth or last octet is designated to identify the host. The preceding octets, typically, are meant to designate the network.