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Tutorials

Free Class A Subnetting Tutorials, IPv4 address Subnetting, How to subnet Class A network

External Resources

This lesson is only a part of a series of IPv4 subnetting lessons. Please visit the below links to learn IPv4 subnetting completely.

• Class C Subnetting Tutorial - Part 1
• Class C Subnetting Tutorial - Part 2
• Class B Subnetting Tutorial - Part 1
• Class B Subnetting Tutorial - Part 2
• Class A Subnetting Tutorial - Part 1
• Class A Subnetting Tutorial - Part 2
• Variable Length Subnet Masking (VLSM)
• Supernetting

In this Class A Subnetting Tutorial - Part 1, you will learn how to subnet a Class A network.

Class A Subnetting

Remember, the first octet of a Class A network is used to represent the network and the remaining three octets are used to represent the host. The default format for a Class A IPv4 address is Network.Host.Host.Host.

Let us consider an example of Class A network 10.0.0.0 - 255.0.0.0. The binary representation of the above network and subnet mask is

 

Component Binary Decimal
Address Part 00001010.00000000.00000000.00000000 10.0.0.0
Subnet Mask 11111111.00000000.00000000.00000000 255.0.0.0

Once again,

If all the bits in the host part are "0", that represents the network address.

If all the bits in the host part are "0" except the last bit, it is the first usable IPv4 address.

If all the bits in the host part are "1" except the last bit, it is the last usable IPv4 address.

If all the bits in the host part are "1", that represents the direct broadcast address.

All the IPv4 addresses between the first and last IPv4 addresses (including the first and last) can be used to configure the devices.

Class A - One Bit Subnetting

If we include one bit from the host part to the network part, the subnet mask is changed into 255.255.128.0 The single bit can have two values in second octet, either 0 or 1.

00001010.0 | 0000000.00000000.00000000
11111111.1 | 0000000.00000000.00000000

That means, we can get two subnets if we do a single bit subnetting. The subnet mask for one bit subnetting is 255.128.0.0.

SN No Description Binaries Decimal
1 Network Address 00001010.00000000.00000000.00000000 10.0.0.0
First IPv4 address 00001010.00000000.00000000.00000001 10.0.0.1
Last IPv4 address 00001010.01111111.11111111.11111110 10.127.255.254
Broadcast Address 100001010.01111111.11111111.11111110 10.127.255.255
2 Network Address 00001010.10000000.00000000.00000000 10.128.0.0
First IPv4 address 00001010.10000000.00000000.00000001 10.128.0.1
Last IPv4 address 00001010.11111111.11111111.11111110 10.255.255.254
Broadcast Address 00001010.11111111.11111111.11111111 10.255.255.255

The network 10.0.0.0 is divided into two networks, each network has 8388608 total IPv4 Addresses and 8388606 usable IPv4 Addresses (two IPv4 Addresses are used in each subnet to represent the network address and the directed broadcast address).

Class A - Two Bit Subnetting

If we include two bits from the host part to the network part, the subnet mask is changed into 255.192.0.0. The two bits added to network part can have four possible values in second octet, 00, 01, 10, and 11.

00001010.00 | 000000.00000000.00000000
11111111.11 | 000000.00000000.00000000

That means, we can get four networks if we do a two bit subnetting. The subnet mask for two bit subnetting is 255.192.0.0.

SN No Description Binaries Decimal
1 Network Address 00001010.00000000.00000000.00000000 10.0.0.0
First IPv4 address 00001010.00000000.00000000.00000001 10.0.0.1
Last IPv4 address 00001010.00111111.11111111.11111110 10.63.255.254
Broadcast Address 00001010.00111111.11111111.11111111 10.63.255.255
2 Network Address 00001010.01000000.00000000.00000000 10.64.0.0
First IPv4 address 00001010.01000000.00000000.00000001 10.64.0.1
Last IPv4 address 00001010.01111111.11111111.11111110 10.127.255.254
Broadcast Address 00001010.01111111.11111111.11111110 10.127.255.255
3 Network Address 00001010.10000000.00000000.00000000 10.128.0.0
First IPv4 address 00001010.10000000.00000000.00000001 10.128.0.1
Last IPv4 address 00001010.10111111.11111111.11111110 10.191.255.254
Broadcast Address 00001010.10111111.11111111.11111111 10.191.255.255
4 Network Address 00001010.11000000.00000000.00000000 10.192.0.0
First IPv4 address 00001010.11000000.00000000.00000001 10.192.0.1
Last IPv4 address 00001010.11111111.11111111.11111110 10.255.255.254
Broadcast Address 00001010.11111111.11111111.11111111 10.255.255.255

The network 10.0.0.0 is divided into four networks, each network has 4194304 total IPv4 Addresses and 4194302 usable IPv4 Addresses (two IPv4 Addresses are used in each subnet to represent the network address and the directed broadcast address).

Class A - 3 Bit Subnetting

If we include three bits from the host part to the network part, the subnet mask is changed into 255.224.0.0 The three bits added to network part can have eight possible values in the second octet and that are 000, 001, 010, and 011, 100, 101, 110 and 111.

00001010.000 | 00000.00000000.00000000
11111111.111 | 00000.00000000.00000000

That means, we can get eight networks if we do a three bit subnetting and the subnet mask will be 255.224.0.0.

SN No Description Binaries Decimal
1 Network Address 00001010.00000000.00000000.00000000 10.0.0.0
First IPv4 address 00001010.00000000.00000000.00000001 10.0.0.1
Last IPv4 address 00001010.00011111.11111111.11111110 10.31.255.254
Broadcast Address 00001010.00011111.11111111.11111111 10.31.255.255
2 Network Address 00001010.00100000.00000000.00000000 10.32.0.0
First IPv4 address 00001010.00100000.00000000.00000001 10.32.0.1
Last IPv4 address 00001010.00111111.11111111.11111110 10.63.255.254
Broadcast Address 00001010.00111111.11111111.11111111 10.63.255.255
3 Network Address 00001010.01000000.00000000.00000000 10.64.0.0
First IPv4 address 00001010.01000000.00000000.00000001 10.64.0.1
Last IPv4 address 00001010.01011111.11111111.11111110 10.95.255.254
Broadcast Address 00001010.01011111.11111111.11111111 10.95.255.255
4 Network Address 00001010.01100000.00000000.00000000 10.96.0.0
First IPv4 address 00001010.01100000.00000000.00000001 10.96.0.1
Last IPv4 address 00001010.01111111.11111111.11111110 10.127.255.254
Broadcast Address 00001010.01111111.11111111.11111111 10.127.255.255
5 Network Address 00001010.10000000.00000000.00000000 10.128.0.0
First IPv4 address 00001010.10000000.00000000.00000001 10.128.0.1
Last IPv4 address 00001010.10011111.11111111.11111110 10.159.255.254
Broadcast Address 00001010.10011111.11111111.11111111 10.159.255.255
6 Network Address 00001010.10100000.00000000.00000000 10.160.0.0
First IPv4 address 00001010.10100000.00000000.00000001 10.160.0.1
Last IPv4 address 00001010.10111111.11111111.11111110 10.191.255.254
Broadcast Address 00001010.10111111.11111111.11111111 10.191.255.255
7 Network Address 00001010.11000000.00000000.00000000 10.192.0.0
First IPv4 address 00001010.11000000.00000000.00000001 10.192.0.1
Last IPv4 address 00001010.11011111.11111111.11111110 10.223.255.254
Broadcast Address 00001010.11011111.11111111.11111111 10.223.255.255
8 Network Address 00001010.11100000.00000000.00000000 10.224.0.0
First IPv4 address 00001010.11100000.00000000.00000001 10.224.0.1
Last IPv4 address 00001010.11111111.11111111.11111110 10.255.255.254
Broadcast Address 00001010.11111111.11111111.11111111 10.255.255.255

The network 10.0.0.0 is divided into eight networks, each network has 2097152 total IPv4 Addresses and 2097150 usable IPv4 Addresses (two IPv4 Addresses are used in each subnet to represent the network address and the directed broadcast address).

In this Class A Subnetting Tutorial - Part 1, you have learned how to subnet a Class A network. Click "Next" to view Class A Subnetting Tutorial - Part 2.

              Jajish Thomason Google+
Related Topics
IPv4 Addresses Class C Subnetting Tutorial - Part 1 Class C Subnetting Tutorial - Part 2 Class B Subnetting Tutorial - Part 1 Class B Subnetting Tutorial - Part 2 Class A Subnetting Tutorial - Part 2 Variable Length Subnet Masking (VLSM) Supernetting
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