Meaning – The term Host ID, refers to the Internet suite of protocols, that part of the IP address that defines the host system on the network. The length of the host ID depends on the type of network or network class (A, B, or C).
It is the portion of an IP address that uniquely identifies a host on a given TCP/IP network. You find the host ID by logically NANDing the binary form of the IP address with the binary form of the subnet mask for the network. The other part of an IP address is the network ID, which specifies the network to which the host belongs.
Example of usage – “The host ID uniquely identifies the host, but only within the boundary of the network ID for the network on which the host is installed.”