In this Class B Subnetting Tutorial - Part 1, you will learn how to subnet a Class B network.
Class B Subnetting
Remember, the first two octets of a Class B network is used to represent the network and the last two octets are used to represent the host. The default format for a Class B IP address is Network.Network.Host.Host.
Let us consider an example of Class B network 172.16.0.0 - 255.255.0.0. The binary representation of the above network and subnet mask is
| Component |
Binary |
Decimal |
| Address Part |
10101100.00010000.00000000.00000000 |
172.16.0.0 |
| SN Mask |
11111111.11111111.00000000.00000000 |
255.255.0.0 |
Once again,
If all the bits in the host part are "0", that represents the network id.
If all the bits in the host part are "0" except the last bit, it is the first usable IP address.
If all the bits in the host part are "1" except the last bit, it is the last usable IP address.
If all the bits in the host part are "1", that represents the direct broadcat address.
All the IP addresses between the first and last IP addresses (including the first and last) can be used to configure the devices.
Class B - 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 third octet, either 0 or 1.
10101100.00010000.0 | 0000000.00000000
11111111.11111111.1 | 0000000.00000000
That means, we can get two subnets if we do a single bit subnetting.
| SN No |
Description |
Binaries
|
Decimal |
| 1 |
Network Address |
10101100.00010000.00000000.00000000 |
172.16.0.0 |
| First IP Address |
10101100.00010000.00000000.00000001 |
172.16.0.1 |
| Last IP Address |
10101100.00010000.01111111.11111110 |
172.16.127.254 |
| Broadcast Address |
10101100.00010000.01111111.11111111 |
172.16.127.255 |
| 2 |
Network Address |
10101100.00010000.10000000.00000000 |
172.16.128.0 |
| First IP Address |
10101100.00010000.10000000.00000001 |
172.16.128.1 |
| Last IP Address |
10101100.00010000.11111111.11111110 |
172.16.255.254 |
| Broadcast Address |
10101100.00010000.11111111.11111111 |
172.16.255.255 |
The network 172.16.0.0 is divided into two networks, each network has 32768 total IP addresses and 32766 usable IP addresses (two IP addresses are used in each subnet to represent the netwok id and the broadcast id). The subnet mask for one bit subnetting is 255.255.128.0.
Class B - Two Bit Subnetting
If we include two bits from the host part to the network part, the subnet mask is changed into 255.255.192.0. The two bits added to network part can have four possible values in third octet, 00, 01, 10, and 11.
10101100.00010000.00 | 000000.00000000
11111111.11111111.11 | 000000.00000000
That means, we can get four networks if we do a two bit subnetting.
| SN No |
Description |
Binaries
|
Decimal |
| 1 |
Network Address |
10101100.00010000.00000000.00000000 |
172.16.0.0 |
| First IP Address |
10101100.00010000.00000000.00000001 |
172.16.0.1 |
| Last IP Address |
10101100.00010000.00111111.11111110 |
172.16.63.254 |
| Broadcast Address |
10101100.00010000.00111111.11111111 |
172.16.63.255 |
| 2 |
Network Address |
10101100.00010000.01000000.00000000 |
172.16.64.0 |
| First IP Address |
10101100.00010000.01000000.00000001 |
172.16.64.1 |
| Last IP Address |
10101100.00010000.01111111.11111110 |
172.16.127.254 |
| Broadcast Address |
10101100.00010000.01111111.11111111 |
172.16.127.255 |
| 3 |
Network Address |
10101100.00010000.10000000.00000000 |
172.16.128.0 |
| First IP Address |
10101100.00010000.10000000.00000001 |
172.16.128.1 |
| Last IP Address |
10101100.00010000.10111111.11111110 |
172.16.191.254 |
| Broadcast Address |
10101100.00010000.10111111.11111111 |
172.16.191.255 |
| 4 |
Network Address |
10101100.00010000.11000000.00000000 |
172.16.192.0 |
| First IP Address |
10101100.00010000.11000000.00000001 |
172.16.192.1 |
| Last IP Address |
10101100.00010000.11111111.11111110 |
172.16.255.254 |
| Broadcast Address |
10101100.00010000.11111111.11111111 |
172.16.255.255 |
The network 172.16.0.0 is divided into four networks, each network has 16384 total IP addresses and 16382 usable IP addresses (two IP addresses are used in each subnet to represent the netwok id and the broadcast id). The subnet mask for one bit subnetting is 255.255.192.0.
Class B - 3 Bit Subnetting
If we include three bits from the host part to the network part, the subnet mask is changed into 255.255.224.0 The three bits added to network part can have eight possible values in the third octet and that are 000, 001, 010, and 011, 100, 101, 110 and 111.
10101100.00010000.000 | 00000.00000000
11111111.11111111.111 | 00000.00000000
That means, we can get eight networks if we do a three bit subnetting.
| SN No |
Description |
Binaries
|
Decimal |
| 1 |
Network Address |
10101100.00010000.00000000.00000000 |
172.16.0.0 |
| First IP Address |
10101100.00010000.00000000.00000001 |
172.16.0.1 |
| Last IP Address |
10101100.00010000.00011111.11111110 |
172.16.31.254 |
| Broadcast Address |
10101100.00010000.00011111.11111111 |
172.16.31.255 |
| 2 |
Network Address |
10101100.00010000.00100000.00000000 |
172.16.32.0 |
| First IP Address |
10101100.00010000.00100000.00000001 |
172.16.32.1 |
| Last IP Address |
10101100.00010000.00111111.11111110 |
172.16.63.254 |
| Broadcast Address |
10101100.00010000.00111111.11111111 |
172.16.63.255 |
| 3 |
Network Address |
10101100.00010000.01000000.00000000 |
172.16.64.0 |
| First IP Address |
10101100.00010000.01000000.00000001 |
172.16.64.1 |
| Last IP Address |
10101100.00010000.01011111.11111110 |
172.16.95.254 |
| Broadcast Address |
10101100.00010000.01011111.11111111 |
172.16.95.255 |
| 4 |
Network Address |
10101100.00010000.01100000.00000000 |
172.16.96.0 |
| First IP Address |
10101100.00010000.01100000.00000001 |
172.16.96.1 |
| Last IP Address |
10101100.00010000.01111111.11111110 |
172.16.127.254 |
| Broadcast Address |
10101100.00010000.01111111.11111111 |
172.16.127.255 |
| 5 |
Network Address |
10101100.00010000.10000000.00000000 |
172.16.128.0 |
| First IP Address |
10101100.00010000.10000000.00000001 |
172.16.128.1 |
| Last IP Address |
10101100.00010000.10011111.11111110 |
172.16.159.254 |
| Broadcast Address |
10101100.00010000.10011111.11111111 |
172.16.159.255 |
| 6 |
Network Address |
10101100.00010000.10100000.00000000 |
172.16.160.0 |
| First IP Address |
10101100.00010000.10100000.00000001 |
172.16.160.1 |
| Last IP Address |
10101100.00010000.10111111.11111110 |
172.16.191.254 |
| Broadcast Address |
10101100.00010000.10111111.11111111 |
172.16.191.255 |
| 7 |
Network Address |
10101100.00010000.11000000.00000000 |
172.16.192.0 |
| First IP Address |
10101100.00010000.11000000.00000001 |
172.16.192.1 |
| Last IP Address |
10101100.00010000.11011111.11111110 |
172.16.223.254 |
| Broadcast Address |
10101100.00010000.11011111.11111111 |
172.16.223.255 |
| 8 |
Network Address |
10101100.00010000.11100000.00000000 |
172.16.224.0 |
| First IP Address |
10101100.00010000.11100000.00000001 |
172.16.224.1 |
| Last IP Address |
10101100.00010000.11111111.11111110 |
172.16.255.254 |
| Broadcast Address |
10101100.00010000.11111111.11111111 |
172.16.255.255 |
The network 172.16.0.0 is divided into eight networks, each network has 8192 total IP addresses and 8190 usable IP addresses (two IP addresses are used in each subnet to represent the netwok id and the broadcast id).
In this Class B Subnetting Tutorial - Part 1, you have learned how to subnet a Class B network. Click "Next" to view Class B Subnetting Tutorial - Part 2.
Related Topics...
• IP Addresses
• Class C Subnetting Tutorial - Part 1
• Class C Subnetting Tutorial - Part 2
• Class B Subnetting Tutorial - Part 2
• Class A Subnetting Tutorial - Part 1
• Class A Subnetting Tutorial - Part 2
• Variable Length Subnet Masking (VLSM)
• Supernetting
