Network addresses are often designed to be unique across the network, although some networks allow for relative or local addresses that may not be unique.
More than one type of network address may be used in any one network.
In some cases terminal nodes may have more than one network address, for example, each link interface may be uniquely identified. In addition, non terminal nodes are often assigned network addresses. Further, because protocols are frequently layered, more than one protocol's network address can occur in any particular network interface or node.
Examples of network addresses are: a telephone number in the public switched telephone network, an Internet Protocol address in the Internet, an IPX address in a local area network, an X.25/X.21 address in a circuit-switched data network, a MAC address in an Ethernet network segment.