Defines network and host portions.

Network segment's unique identifying address.

Identifier for subdivision of network.

In network security a screened subnet refers to the use of one or more logical screening routers as a firewall to define three separate subnets: an external router (sometimes called an access router), that separates the external network from a perimeter network, and an internal router (sometimes called a choke router) that separates the perimeter network from the internal network.

Customizable subnet mask for efficiency.

an option in the Extension Mechanisms for DNS that allows a recursive DNS resolver to specify the subnetwork for the host or client on whose behalf it is making a DNS query.