Chris Hall bio photo

Chris Hall

Adjusting technology to make it fit my requirements...

Windows, Linux, Virtualisation, Unified Computing & Cloud Offerings Design Engineer.

PolarCloudsUK Chris Google+ LinkedIn Github

OK, a tad of a “dry” subject, but hardly a week goes by without having to Google myself a subnet cheat sheet. Saves me from having to work this out manually! No need to Google anymore.

Here is a cheat sheet here for good keeping and future reference. The /30 table is especially handy for those using client specific overrides with OpenVPN :o)

Overview

CIDR Breakdown

CIDR Total IPs Usable IPs Netmask Amount of a Class C
/32 1 1 255.255.255.255 1/256
/31 2 2* 255.255.255.254 1/128
/30 4 2 255.255.255.252 1/64
/29 8 6 255.255.255.248 1/32
/28 16 14 255.255.255.240 1/16
/27 32 30 255.255.255.224 1/8
/26 64 62 255.255.255.192 1/4
/25 128 126 255.255.255.128 1/2
/24 256 254 255.255.255.0 1
/23 512 510 255.255.254.0 2
/22 1024 1022 255.255.252.0 4
/21 2048 2046 255.255.248.0 8
/20 4096 4094 255.255.240.0 16
/19 8192 8190 255.255.224.0 32
/18 16384 16382 255.255.192.0 64
/17 32768 32766 255.255.128.0 128
/16 65536 65534 255.255.0.0 256
/15 131,072 131,070 255.254.0.0 512
/14 262,144 262,142 255.252.0.0 1024
/13 524,288 524,286 255.248.0.0 2048
/12 1,048,576 1,048,574 255.240.0.0 4096
/11 2,097,152 2,097,150 255.224.0.0 8192
/10 4,194,304 4,194,302 255.192.0.0 16,384
/9 8,388,608 8,388,606 255.128.0.0 32,768
/8 16,777,216 16,777,214 255.0.0.0 65,536
/7 33,554,432 33,554,430 254.0.0.0 131,072
/6 67,108,864 67,108,862 252.0.0.0 262,144
/5 134,217,728 134,217,726 248.0.0.0 524,288
/4 268,435,456 268,435,454 240.0.0.0 1,048,576
/3 536,870,912 536,870,910 224.0.0.0 2,097,152
/2 1,073,741,824 1,073,741,822 192.0.0.0 4,194,304
/1 2,147,483,648 2,147,483,646 128.0.0.0 8,388,608

*See rfc3021

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

Network # Usable IPs Broadcast
.0 .1-.126 .127
.128 .129-.254 .255

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

Network # Usable IPs Broadcast
.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 IPs Broadcast
.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 IPs Broadcast
.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 IPs Broadcast
.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 IPs Broadcast
.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

-Chris