Subnetting class B
L
earning Class B subnetting can be made easier by following a structured approach
that builds on the basic principles of IP addressing and subnetting. Here's a step-by-
step guide to understanding and practicing Class B subnetting:
Step-by-Step Guide to Learning Class B Subnetting
1. Understand the Basics of Class B Networks
Default Subnet Mask: 255.255.0.0 (or /16 in CIDR notation)
IP Address Range: 128.0.0.0 to 191.255.255.255
Number of Host Addresses: 65,536 addresses, with 65,534 usable addresses (the
first address is the network address, and the last is the broadcast address)
2. Understand Binary Representation
Knowing how to convert between binary and decimal is crucial for subnetting. Here's a
quick refresher:
Binary to Decimal Conversion: For example, the binary number 11000000 can be
converted to decimal by summing the powers of 2 that correspond to the positions of
the 1s.
7 6 5 4 3 2 1 0
o 1⋅2 +1⋅2 +0⋅2 +0⋅2 +0⋅2 +0⋅2 +0⋅2 +0⋅2 = 128+64+0+0+0+0+0+0=192
3. Subnetting Principles
Subnetting involves borrowing bits from the host portion of the IP address to create
additional subnets. For a Class B network, the default subnet mask is 255.255.0.0, which
leaves 16 bits for host addresses. By changing the subnet mask, you can create more subnets
at the expense of fewer host addresses per subnet.
4. Calculate the Number of Subnets and Hosts
Use the following formulas:
Number of Subnets: 2n (where “n” is the number of bits borrowed from the host
portion)
Number of Hosts per Subnet: 2h − 2 (where “h” is the number of bits remaining for
the host portion)
5. Practice with Examples
Example 1: Subnetting a Class B Network to Create 4 Subnets
1. Determine the number of bits to borrow:
To create 4 subnets, you need 22=4 subnets, so you borrow 2 bits from the host
portion.
L
earning Class B subnetting can be made easier by following a structured approach
that builds on the basic principles of IP addressing and subnetting. Here's a step-by-
step guide to understanding and practicing Class B subnetting:
Step-by-Step Guide to Learning Class B Subnetting
1. Understand the Basics of Class B Networks
Default Subnet Mask: 255.255.0.0 (or /16 in CIDR notation)
IP Address Range: 128.0.0.0 to 191.255.255.255
Number of Host Addresses: 65,536 addresses, with 65,534 usable addresses (the
first address is the network address, and the last is the broadcast address)
2. Understand Binary Representation
Knowing how to convert between binary and decimal is crucial for subnetting. Here's a
quick refresher:
Binary to Decimal Conversion: For example, the binary number 11000000 can be
converted to decimal by summing the powers of 2 that correspond to the positions of
the 1s.
7 6 5 4 3 2 1 0
o 1⋅2 +1⋅2 +0⋅2 +0⋅2 +0⋅2 +0⋅2 +0⋅2 +0⋅2 = 128+64+0+0+0+0+0+0=192
3. Subnetting Principles
Subnetting involves borrowing bits from the host portion of the IP address to create
additional subnets. For a Class B network, the default subnet mask is 255.255.0.0, which
leaves 16 bits for host addresses. By changing the subnet mask, you can create more subnets
at the expense of fewer host addresses per subnet.
4. Calculate the Number of Subnets and Hosts
Use the following formulas:
Number of Subnets: 2n (where “n” is the number of bits borrowed from the host
portion)
Number of Hosts per Subnet: 2h − 2 (where “h” is the number of bits remaining for
the host portion)
5. Practice with Examples
Example 1: Subnetting a Class B Network to Create 4 Subnets
1. Determine the number of bits to borrow:
To create 4 subnets, you need 22=4 subnets, so you borrow 2 bits from the host
portion.
