Class A Number of Bits Borrowed Subnet Effective Number of Number of Subnet from Host Portion Mask Subnets Hosts/Subnet Mask Bits ------- --------------- --------- ------------- ------------- 1 255.128.0.0 2 8388606 /9 2 255.192.0.0 4 4194302 /10 3 255.224.0.0 8 2097150 /11 4 255.240.0.0 16 1048574 /12 5 255.248.0.0 32 524286 /13 6 255.252.0.0 64 262142 /14 7 255.254.0.0 128 131070 /15 8 255.255.0.0 256 65534 /16 9 255.255.128.0 512 32766 /17 10 255.255.192.0 1024 16382 /18 11 255.255.224.0 2048 8190 /19 12 255.255.240.0 4096 4094 /20 13 255.255.248.0 8192 2046 /21 14 255.255.252.0 16384 1022 /22 15 255.255.254.0 32768 510 /23 16 255.255.255.0 65536 254 /24 17 255.255.255.128 131072 126 /25 18 255.255.255.192 262144 62 /26 19 255.255.255.224 524288 30 /27 20 255.255.255.240 1048576 14 /28 21 255.255.255.248 2097152 6 /29 22 255.255.255.252 4194304 2 /30 23 255.255.255.254 8388608 2* /31
Class B Number of Bits Borrowed Subnet Effective Number of Number of Subnet from Host Portion Mask Subnets Hosts/Subnet Mask Bits ------- --------------- --------- ------------- ------------- 1 255.255.128.0 2 32766 /17 2 255.255.192.0 4 16382 /18 3 255.255.224.0 8 8190 /19 4 255.255.240.0 16 4094 /20 5 255.255.248.0 32 2046 /21 6 255.255.252.0 64 1022 /22 7 255.255.254.0 128 510 /23 8 255.255.255.0 256 254 /24 9 255.255.255.128 512 126 /25 10 255.255.255.192 1024 62 /26 11 255.255.255.224 2048 30 /27 12 255.255.255.240 4096 14 /28 13 255.255.255.248 8192 6 /29 14 255.255.255.252 16384 2 /30 15 255.255.255.254 32768 2* /31
Class C Number of Bits Borrowed Subnet Effective Number of Number of Subnet from Host Portion Mask Subnets Hosts/Subnet Mask Bits ------- --------------- --------- ------------- ------------- 1 255.255.255.128 2 126 /25 2 255.255.255.192 4 62 /26 3 255.255.255.224 8 30 /27 4 255.255.255.240 16 14 /28 5 255.255.255.248 32 6 /29 6 255.255.255.252 64 2 /30 7 255.255.255.254 128 2* /31