## VLSM/CIDR Reference Table (IPv4 Subnetting Chart) | Class | Prefix | Subnet Mask | Subnets | Hosts / Usable IPs | Bits used | | ----- | ------ | --------------- | ------- | ------------------ | --------- | | C | /31 | 255.255.255.254 | 128 | 2 (ppp only) | 7 / 1 | | ^ | /30 | 255.255.255.252 | 64 | 4 (2) | 6 / 2 | | ^ | /29 | 255.255.255.248 | 32 | 8 (6) | 5 / 3 | | ^ | /28 | 255.255.255.240 | 16 | 16 (14) | 4 / 4 | | ^ | /27 | 255.255.255.224 | 8 | 32 (30) | 3 / 5 | | ^ | /26 | 255.255.255.192 | 4 | 64 (62) | 2 / 6 | | ^ | /25 | 255.255.255.128 | 2 | 128 (126) | 1 / 7 | | ^ | /24 | 255.255.255.0 | 0 | 256 (254) | 0 / 8 | | B | /23 | 255.255.254.0 | 128 | 512 (510) | 7 / 9 | | ^ | /22 | 255.255.252.0 | 64 | 1024 (1022) | 6 / 10 | | ^ | /21 | 255.255.248.0 | 32 | 2048 (2046) | 5 / 11 | | ^ | /20 | 255.255.240.0 | 16 | 4096 (4094) | 4 / 12 | | ^ | /19 | 255.255.224.0 | 8 | 8292 (8290) | 3 / 13 | | ^ | /18 | 255.255.192.0 | 4 | 16384 (16382) | 2 / 14 | | ^ | /17 | 255.255.128.0 | 2 | 32768 (32766) | 1 / 15 | | ^ | /16 | 255.255.0.0 | 0 | 65536 (65534) | 0 / 16 | | A | /15 | 255.254.0.0 | 128 | 131072 (- 2) | 7 / 17 | | ^ | /14 | 255.252.0.0 | 64 | 262144 (- 2) | 6 / 18 | | ^ | /13 | 255.248.0.0 | 32 | 524288 (- 2) | 5 / 19 | | ^ | /12 | 255.240.0.0 | 16 | 1048576 (- 2) | 4 / 20 | | ^ | /11 | 255.224.0.0 | 8 | 2097152 (- 2) | 3 / 21 | | ^ | /10 | 255.192.0.0 | 4 | 4194304 (- 2) | 2 / 22 | | ^ | /9 | 255.128.0.0 | 2 | 8388608 (- 2) | 1 / 23 | | ^ | /8 | 255.0.0.0 | 0 | 16777216 (- 2) | 0 / 24 |