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About Subnetting

When using port forwarding, you need a reasonable knowledge of how network and subnets work to successfully set this up. Networks may be divided into the subnets shown below by increasing the subnet mask successively by one bit. This affects the total number of hosts that can be addressed in the networks (last column).

Route as follows:

Prefix Size Network Mask Total IPs Usable IPs
/32 255.255.255.255 1 1
/31 255.255.255.254 2 0
/30 255.255.255.252 4 2
/29 255.255.255.248 8 6
/28 255.255.255.240 16 14
/27 255.255.255.224 32 30
/26 255.255.255.192 64 62
/25 255.255.255.128 128 126
/24 255.255.255.0 256 254
/23 255.255.254.0 512 510
/22 255.255.252.0 1024 1022
/21 255.255.248.0 2048 2046
/20 255.255.240.0 4096 4094
/19 255.255.224.0 8192 8190
/18 255.255.192.0 16384 16382
/17 255.255.128.0 32768 32766
/16 255.255.0.0 65536 65534
/15 255.254.0.0 131072 131070
/14 255.252.0.0 262144 262142
/13 255.248.0.0 524288 524286
/12 255.240.0.0 1048576 1048574
/11 255.224.0.0 2097152 2097150
/10 255.192.0.0 4194304 4194302
/9 255.128.0.0 8388608 8388606
/8 255.0.0.0 16777216 16777214
/7 254.0.0.0 33554432 33554430
/6 252.0.0.0 67108864 67108862
/5 248.0.0.0 33554432 33554430
/4 240.0.0.0 268435456 268435454
/3 224.0.0.0 536870912 536870910
/2 192.0.0.0 1073741824 1073741822
/1 128.0.0.0 2147483648 2147483646
/0 0.0.0.0 4294967296 4294967294

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