Subnet Cheat Sheet

Overview

CIDR Breakdown

CIDRTotal IPsUsable IPsNetmaskAmount of a Class C
/3211255.255.255.2551/256
/3122*255.255.255.2541/128
/3042255.255.255.2521/64
/2986255.255.255.2481/32
/281614255.255.255.2401/16
/273230255.255.255.2241/8
/266462255.255.255.1921/4
/25128126255.255.255.1281/2
/24256254255.255.255.01
/23512510255.255.254.02
/2210241022255.255.252.04
/2120482046255.255.248.08
/2040964094255.255.240.016
/1981928190255.255.224.032
/181638416382255.255.192.064
/173276832766255.255.128.0128
/166553665534255.255.0.0256
/15131,072131,070255.254.0.0512
/14262,144262,142255.252.0.01024
/13524,288524,286255.248.0.02048
/121,048,5761,048,574255.240.0.04096
/112,097,1522,097,150255.224.0.08192
/104,194,3044,194,302255.192.0.016,384
/98,388,6088,388,606255.128.0.032,768
/816,777,21616,777,214255.0.0.065,536
/733,554,43233,554,430254.0.0.0131,072
/667,108,86467,108,862252.0.0.0262,144
/5134,217,728134,217,726248.0.0.0524,288
/4268,435,456268,435,454240.0.0.01,048,576
/3536,870,912536,870,910224.0.0.02,097,152
/21,073,741,8241,073,741,822192.0.0.04,194,304
/12,147,483,6482,147,483,646128.0.0.08,388,608

*See rfc3021

 

/25 (255.255.255.128), 2 Subnets, 126 Usable IPs per Subnet

Network #Usable IPsBroadcast
.0.1-.126.127
.128.129-.254.255

 

/26 (255.255.255.192), 4 Subnets, 62 Usable IPs per Subnet

Network #Usable IPsBroadcast
.0.1-.62.63
.64.65-.126.127
.128.129-.190.191
.192.193-.254.255

 

/27 (255.255.255.224), 8 Subnets, 30 Usable IPs per Subnet

Network #Usable IPsBroadcast
.0.1-.30.31
.32.33-.62.63
.64.65-.94.95
.96.97-.126.127
.128.129-.158.159
.160.161-.190.191
.192.193-.222.223
.224.225-.254.255

 

/28 (255.255.255.240), 16 Subnets, 14 Usable IPs per Subnet

Network #Usable IPsBroadcast
.0.1-.14.15
.16.17-.30.31
.32.33-.46.47
.48.49-.62.63
.64.65-.78.79
.80.81-.94.95
.96.97-.110.111
.112.113-.126.127
.128.129-.142.143
.144.145-.158.159
.160.161-.174.175
.176.177-.190.191
.192.193-.206.207
.208.209-.222.223
.224.225-.238.239
.240.241-.254.255

 

/29 (255.255.255.248), 32 Subnets, 6 Usable IPs per Subnet

Network #Usable IPsBroadcast
.0.1-.6.7
.8.9-.14.15
.16.17-.22.23
.24.25-.30.31
.32.33-.38.39
.40.41-.46.47
.48.49-.54.55
.56.57-.62.63
.64.65-.70.71
.72.73-.78.79
.80.81-.86.87
.88.89-.94.95
.96.97-.102.103
.104.105-.110.111
.112.113-.118.119
.120.121-.126.127
.128.129-.134.135
.136.137-.142.143
.144.145-.150.151
.152.153-.158.159
.160.161-.166.167
.168.169-.174.175
.176.177-.182.183
.184.185-.190.191
.192.193-.198.199
.200.201-.206.207
.208.209-.214.215
.216.217-.222.223
.224.225-.230.231
.232.233-.238.239
.240.241-.246.247
.248.249-.254.255

 

/30 (255.255.255.252), 64 Subnets, 2 Usable IPs per Subnet

Network #Usable IPsBroadcast
.0.1-.2.3
.4.5-.6.7
.8.9-.10.11
.12.13-.14.15
.16.17-.18.19
.20.21-.22.23
.24.25-.26.27
.28.29-.30.31
.32.33-.34.35
.36.37-.38.39
.40.41-.42.43
.44.45-.46.47
.48.49-.50.51
.52.53-.54.55
.56.57-.58.59
.60.61-.62.63
.64.65-.66.67
.68.69-.70.71
.72.73-.74.75
.76.77-.78.79
.80.81-.82.83
.84.85-.86.87
.88.89-.90.91
.92.93-.94.95
.96.97-.98.99
.100.101-.102.103
.104.105-.106.107
.108.109-.110.111
.112.113-.114.115
.116.117-.118.119
.120.121-.122.123
.124.125-.126.127
.128.129-.130.131
.132.133-.134.135
.136.137-.138.139
.140.141-.142.143
.144.145-.146.147
.148.149-.150.151
.152.153-.154.155
.156.157-.158.159
.160.161-.162.163
.164.165-.166.167
.168.169-.170.171
.172.173-.174.175
.176.177-.178.179
.180.181-.182.183
.184.185-.186.187
.188.189-.190.191
.192.193-.194.195
.196.197-.198.199
.200.201-.202.203
.204.205-.206.207
.208.209-.210.211
.212.213-.214.215
.216.217-.218.219
.220.221-.222.223
.224.225-.226.227
.228.229-.230.231
.232.233-.234.235
.236.237-.238.239
.240.241-.242.243
.244.245-.246.247
.248.249-.250.251
.252.253-.254.255