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Quick Reference: IPv4 Subnet Table

Subnet BitMask
(last octet(s))

Subnet Mask

CIDR*

# of
Addresses
per
Subnet

# of
Hosts
per
Subnet

'Network' Address
(un-usable)

IP Address Ranges
Subnet Addr = Loopback
Last Addr = Broadcast

Broadcast Address
(un-usable)

.00000000.00000000 255.255.0.0 /16 65536 65534 3rd Octet uses same format as /24 4th octet
(same as 256 Class C ranges)
10000000.00000000 255.255.128.0 /17 32768 32766 3rd Octet uses same format as /25 4th octet
(same as 128 Class C ranges)
11000000.00000000 255.255.192.0 /18 16384 16382 3rd Octet uses same format as /26 4th octet
(same as 64 Class C ranges)
11100000.00000000 255.255.224.0 /19 8192 8190 3rd Octet uses same format as /27 4th octet
(same as 32 Class C ranges)
11110000.00000000 255.255.240.0 /20 4096 4094 3rd Octet uses same format as /28 4th octet
(same as 16 Class C ranges)
11111000.00000000 255.255.248.0 /21 2048 2046 3rd Octet uses same format as /29 4th octet
(same as 8 Class C ranges)
11111100.00000000 255.255.252.0 /22 1024 1022 3rd Octet uses same format as /30 4th octet
(same as 4 Class C ranges)
11111110.00000000 255.255.254.0 /23 512 510 3rd Octet uses same format as /31 4th octet
(same as 2 Class C ranges)
.00000000 255.255.255.0 /24 256 254 .0 .1 - .254 .255
.10000000 255.255.255.128 /25 128 126 .0
.128
.1 - .126
.129 - .254
.127
.255
.11000000 255.255.255.192 /26 64 62 .0
.64
.128
.192
.1 - .62
.65 - .126
.129 - .190
.193 - .254
.63
.127
.191
.255
.11100000 255.255.255.224 /27 32 30 .0
.32
.64
.96
.128
.160
.192
.224
.1 - .30
.33 - .62
.65 - .94
.97 - .126
.129 - .158
.161 - .190
.193 - .222
.225 - .254
.31
.63
.95
.127
.159
.191
.223
.255
.11110000 255.255.255.240 /28 16 14 .0
.16
.32
.48
.64
.80
.96
.112
.128
.144
.160
.176
.192
.208
.224
.240
.1 - 14
.17 - .30
.33 - .46
.49 - .62
.65 - .78
.81 - .94
.97 - .110
.113 - .127
.129 - .142
.145 - .159
.161 - .174
.177 - .190
.193 - .206
.209 - .222
.225 - .238
.241 - .254
.15
.31
.47
.63
.79
.95
.111
128
143
160
175
191
207
223
239
255
.11111000 255.255.255.248 /29 8 6 .0
.8
.16
.24
.32
.40
.48
.56
.64
.72
.80
.88
.96
.104
.112
.120
.128
.136
.144
.152
.160
.168
.176
.184
.192
.200
.208
.216
.224
.232
.240
.248
.1 - .6
.9 - 14
.17 - 22
.25 - 30
.33 - 38
.41 - 46
.49 - 54
.57 - 62
.65 - 70
.73 - 78
.81 - 86
.89 - 94
.97 - 102
.105 - 110
.113 - 118
.121 - 126
.129 - 134
.137 - 142
.145 - 150
.153 - 158
.161 - 166
.169 - 174
.177 - 182
.185 - 190
.193 - 198
.201 - 206
.209 - 214
.217 - 222
.225 - 230
.233 - 238
.241 - 246
.249 - 254
.7
.15
.23
.31
.39
.47
.55
.63
.71
.79
.87
.95
.103
.111
.119
.127
.135
.143
.151
.159
.167
.175
.183
.191
.199
.207
.215
.223
.231
.239
.247
.255
.11111100 255.255.255.252 /30 4 2 .0
.4
.8
.12
.16
.20
.24
.28
.32
.36
.40
.44
.48
.52
.56
.60
.64
.68
.72
.76
.80
.84
.88
.92
.96
.100
.104
.108
.112
.116
.120
.124
.128
.132
.136
.140
.144
.148
.152
.156
.160
.164
.168
.172
.176
.180
.184
.188
.192
.196
.200
.204
.208
.212
.216
.220
.224
.228
.232
.236
.240
.244
.248
.252
.1 - .2
.5 - .6
.9 - .10
.13 - .14
.17 - .18
.21 - .22
.25 - .26
.29 - .30
.33 - .34
.37 - .37
.41 - .42
.45 - .46
.49 - .50
.53 - .54
.57 - .58
.61 - .62
.65 - .66
.69 - .70
.73 - .74
.77 - .78
.81 - .82
.85 - .86
.89 - .90
.93 - .94
.97 - .98
.101 - .102
.105 - .106
.109 - .110
.113 - .114
.117 - .118
.121 - .122
.125 - .126
.129 - .130
.133 - .134
.137 - .138
.141 - .142
.145 - .146
.149 - .150
.153 - .154
.157 - .158
.161 - .162
.165 - .166
.169 - .170
.173 - .174
.177 - .178
.181 - .182
.185 - .186
.189 - .190
.193 - .194
.197 - .199
.201 - .202
.205 - .206
.209 - .210
.213 - .214
.217 - .218
.221 - .222
.225 - .226
.229 - .230
.233 - .234
.237 - .238
.241 - .242
.245 - .246
.249 - .250
.253 - .254
.3
.7
.11
.15
.19
.23
.27
.31
.35
.39
.43
.47
.51
.55
.59
.63
.67
.71
.75
.79
.83
.87
.91
.95
.99
.103
.107
.111
.115
.119
.123
.127
.131
.135
.139
.143
.147
.151
.155
.159
.163
.167
.171
.175
.179
.183
.187
.191
.195
.199
.203
.207
.211
.215
.219
.223
.227
.231
.235
.239
.243
.247
.251
.255
11111110 255.255.255.254 /31 2 0 Unusable
11111111 255.255.255.255 /32 1 1 Host (single address)

*CIDR = Classless Inter-Domain Routing