Network+ Subnetting Cheat Sheet

network and broadcast address dont count towards usable IPs

CIDR /24

Subnet Mask: 255.255.255.0

Total IPs: 256

Usable Host: 254

Usable Host Ranges Ex: 192.168.1.1 – 192.168.1.254

CIDR /25

Subnet Mask: 255.255.255.128

Total IPs: 128

Usable Host: 126

Usable Host Ranges Ex: 192.168.1.1 – 192.168.1.126

CIDR /26

Subnet Mask: 255.255.255.192

Total IPs: 64

Usable Host: 62

Usable Host Ranges Ex: 192.168.1.1 – 192.168.1.62

CIDR /27

Subnet Mask: 255.255.255.224

Total IPs: 32

Usable Host: 30

Usable Host Ranges Ex: 192.168.1.1 – 192.168.1.30

CIDR /28

Subnet Mask: 255.255.255.240

Total IPs: 16

Usable Host: 14

Usable Host Ranges Ex: 192.168.1.1 – 192.168.1.14

CIDR /29

Subnet Mask: 255.255.255.248

Total IPs: 8

Usable Host: 6

Usable Host Ranges Ex: 192.168.1.1 – 192.168.1.6

CIDR /30

Subnet Mask: 255.255.255.252

Total IPs: 4

Usable Host: 2

Usable Host Ranges Ex: 192.168.1.1 – 192.168.1.2

CIDR /31

Subnet Mask: 255.255.255.254

Total IPs: 2

Usable Host: 2

Usable Host Ranges Ex: None (used as point-to-point link)

CIDR /32

Subnet Mask: 255.255.255.255

Total IPs: 1

Usable Host: 1

Usable Host Ranges Ex: (single IP only)

Class A

0.0.0.0 – 127.255.255.255

Class B

128.0.0.0 - 191.255.255.255

Class C

192.0.0.0 - 223.255.255.255

Class D

224.0.0.0 - 239.255.255.255

Class E

240.0.0.0 - 255.255.255.255