ITN 101 Subnetting Shortcuts

Defines the range of IP addresses that can be used within a subnet.

Subnet Mask

Represents the number of bits allocated for the network portion of the address in the format IP Address/Prefix Length.

CIDR Notation

Use the formula: /n (where n is the number of bits for the network).

Finding Subnet Mask Formula

Number of Hosts = 2^(32 - subnet bits) - 2.

Determining Number of Hosts Formula

Size = 2^(number of host bits).

Subnet Size Formula

Class A Address Range

0-127 with a subnet mask of 255.0.0.0.

128-191 with a subnet mask of 255.255.0.0.

Class B Address Range

192-223 with a subnet mask of 255.255.255.0.

Class C Address Range

Provides 4 IPs, 2 usable.

CIDR /30

Can be calculated by subtracting the unusual octet in the subnet mask from 256.

Magic Number Calculation

Add the magic number to the last octet of the starting address.

Subnet's Network Address Calculation

Binary Equivalent of 0

0000

Binary Equivalent of 1

0001

Binary Equivalent of 2

0010

Binary Equivalent of 3

0011

Binary Equivalent of 4

0100

Binary Equivalent of 5

0101

Binary Equivalent of 6

0110

Binary Equivalent of 7

0111

Binary Equivalent of 8

1000

Binary Equivalent of 9

1001

Binary Equivalent of 10

Binary Equivalent of 11

Binary Equivalent of 12

Binary Equivalent of 13

Binary Equivalent of 14

Binary Equivalent of 15