What is a Network Address?

A computer network is a group of interconnected computers that share common or different resources provided on or by network nodes. This sharing or communication between the machines is governed by some set of rules or network protocols. These computers or machines are identified by network addresses and may have hostnames.

Introduction to Network Address

A Network Address is a logical or physical address uniquely identifying a host or a machine in a telecommunication network. A network may also not be unique and can contain some structural and hierarchical information of the node in the network. Internet protocol (IP) addresses, Media Access Control (MAC) addresses, and telephone numbers are some basic examples of network addresses. It can be of numeric type symbolic or both in some cases.

Network Addressing

It is the prime responsibility of the network layer to assign unique addresses to different nodes in a network. As mentioned earlier they can be physical or logical but primarily they are logical addresses i.e. software-based addresses.  The most widely used network address is an IP address. It uniquely identifies a node in an IP network. An IP address is a 32-bit long numeric address represented in a form of dot-decimal notation where each byte is written in a decimal form separated by a period. For example 196.32.216.9 is an IP address where 196 represents first 8 bits, 32 next 8 bits and so on. The first three bytes of an IP address represents the network and the last byte specifies the host in the network. An IP address is further divided into sub classes:

Class A

An IP address is assigned to those networks that include large number of hosts.

• The network ID consists of 8 bits.
• The host ID consists of 24 bits.

In Class A, the network ID is determined by the remaining 7 bits, while the first bit in higher order bits of the first octet is always set to 0.

There are a total of 2⁷  networks in Class A, which equals 128 network addresses.

 2²⁴ - 2 = 16,777,214 host addresses make up the entire number of hosts in Class A.

Class B

An IP address is assigned to networks range from small sized to large sized.

Class B networks are those that range in size from small to large networks and are given an IP address.

• There are 16 bits in the Network ID.
• There are 16 bits in the host ID.

In Class B, the network ID is determined by the remaining 14 bits, with the higher order bits of the first octet always set to 10. The Host ID is found in the remaining 16 bits.

There are  2¹⁴ networks in Class B, which equates to 16384 network addresses.

Class C

An IP address is assigned to networks that are small sized.

• There are 24 bits in the Network ID.
• The host ID consists of 8 bits.

In Class C, the network ID is determined by the final 21 bits, with the higher order bits of the first octet always set to 110. The host in a network is identified by its eight bits, or host ID.

There are 2²¹  networks in all, which equals 2097152 network addresses.

There are a total of 2⁸ - 2 = 254 host addresses.

Class D

IP address are reserved for multicast address and does not possess subnetting. Multicast addresses are assigned a reserved IP address in Class D. It is a empty part of subnetting. In every network, the host ID is determined by the remaining bits, with the higher order bits of the first octet always set to 1110.

Class E  

An IP address is used for the future use and for the research and development purposes and does not possess any subnetting. An IP address is utilized in Class E for research and development or future use. There is no subnetting on it. In every network, the host ID is determined by the remaining bits, with the higher order bits of the first octet always set to 1111.

An IP address is divided into two parts:

1. Net ID :  represents the number of networks.
2. Host ID : represents the number of hosts.

Norms to assign Network ID

• For the hosts located in the same network, share the same network ID.
• It cannot start with 127 as 127 is used exclusively by Class A.
• If all the bits of the network ID are set to 0, it could not be assigned as it specifies a particular host on the local network.
• If all the bits of the network ID are set to 1, it could not be assigned as it is reserved for multicast address.

Norms to assign Host ID

• It must be unique within any network.
• If all the bits of the host ID are set to 0, it could not be assigned as it is used to represent the network ID of the IP address.
• The Host ID with all the bits set to 1 are reserved for multicast address.

Classful Network Addressing

For more on network addressing and architecture refer to Introduction of Classful Addressing