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A network address in IPv4 is a special address which is used to uniquely identify a network. Routers use network address to identify a network. Routing table (a table maintained by routers) contain network addresses and additional information about how to reach that network.

A network address is a special IPv4 address where all host bits zero.

Let’s learn what is network address with examples of Class A, Class B and Class C IPv4 networks. Default subnet masks of Class A, Class B and Class C networks are given below.

• For Class A network, the first octet belongs to the network part and remaining three octets belongs to the host part. So, the default subnet mask of a Class A network is 255.0.0.0.
• For Class B network, the first two octets belongs to the network part and remaining two octets belongs to the host part. So, the default subnet mask of a Class B network is 255.255.0.0.
• For Class C network, the first three octets belongs to the network part and remaining one octet belongs to the host part. So, the default subnet mask of a Class B network is 255.255.255.0.

To understand the concept clearly, refer below image.

## Network address of a Class A network

Let us take an example of IPv4 Class A network 10.0.0.0. Note that 10.0.0.0 is the first IPv4 address in its block. We have already learned that for Class A network, first octet belongs to network part and remaining three octets belongs to the host part. So, the default subnet mask of a Class A network is 255.0.0.0.

The network address 10.0.0.0 is obtained by keeping all host bits as binary number "0". Please refer below image.

## Network address of a Class B network

Let us take an example of IPv4 Class B network 172.16.0.0. Note that 172.16.0.0 is the first IPv4 address in its block. We have already learned that for Class B network, first two octets belongs to network part and remaining two octets belongs to the host part. So, the default subnet mask of a Class B network is 255.255.0.0.

The network address 172.16.0.0 is obtained by keeping all host bits as binary number "0". Please refer below image.

## Network address of a Class C network

Let us take an example of IPv4 Class C network 192.168.0.0. Note that 192.168.0.0 is the first IPv4 address in its block. We have already learned that for Class C network, first three octets belongs to network part and remaining one octet belongs to the host part. So, the default subnet mask of a Class C network is 255.255.255.0.

The network address 192.168.0.0 is obtained by keeping all host bits as binary number "0". Please refer below image.