Subnet Mask Crib Sheet
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| CIDR (Bits) |
Net Mask | Hosts [1] | Class | ||
|---|---|---|---|---|---|
| Decimal | Hexadecimal | Binary | |||
| 1 | 128.0.0.0 | 80.00.00.00 | 0000 0000 . 0000 0000 . 0000 0000 . 0000 0000 |
2,147,483,646 | |
| 2 | 192.0.0.0 | C0.00.00.00 | 1000 0000 . 0000 0000 . 0000 0000 . 0000 0000 |
1,073,741,822 | |
| 3 | 224.0.0.0 | E0.00.00.00 | 1110 0000 . 0000 0000 . 0000 0000 . 0000 0000 |
536,870,910 | |
| 4 | 240.0.0.0 | F0.00.00.00 | 1111 0000 . 0000 0000 . 0000 0000 . 0000 0000 |
268,435,454 | |
| 5 | 248.0.0.0 | F8.00.00.00 | 1111 1000 . 0000 0000 . 0000 0000 . 0000 0000 |
134,217,726 | |
| 6 | 252.0.0.0 | FC.00.00.00 | 1111 1100 . 0000 0000 . 0000 0000 . 0000 0000 |
67,108,862 | |
| 7 | 254.0.0.0 | FE.00.00.00 | 1111 1110 . 0000 0000 . 0000 0000 . 0000 0000 |
33,554,430 | |
| 8 | 255.0.0.0 | FF.00.00.00 | 1111 1111 . 0000 0000 . 0000 0000 . 0000 0000 |
16,777,214 | Class A |
| 9 | 255.128.0.0 | FF.80.00.00 | 1111 1111 . 1000 0000 . 0000 0000 . 0000 0000 |
8,388,606 | |
| 10 | 255.192.0.0 | FF.C0.00.00 | 1111 1111 . 1100 0000 . 0000 0000 . 0000 0000 |
4,194,302 | |
| 11 | 255.224.0.0 | FF.E0.00.00 | 1111 1111 . 1110 0000 . 0000 0000 . 0000 0000 |
2,097,150 | |
| 12 | 255.240.0.0 | FF.F0.00.00 | 1111 1111 . 1111 0000 . 0000 0000 . 0000 0000 |
1,048,574 | |
| 13 | 255.248.0.0 | FF.F8.00.00 | 1111 1111 . 1111 1000 . 0000 0000 . 0000 0000 |
524,286 | |
| 14 | 255.252.0.0 | FF.FC.00.00 | 1111 1111 . 1111 1100 . 0000 0000 . 0000 0000 |
262,142 | |
| 15 | 255.254.0.0 | FF.FE.00.00 | 1111 1111 . 1111 1110 . 0000 0000 . 0000 0000 |
131,070 | |
| 16 | 255.255.0.0 | FF.FF.00.00 | 1111 1111 . 1111 1111 . 0000 0000 . 0000 0000 |
65,534 | Class B |
| 17 | 255.255.128.0 | FF.FF.80.00 | 1111 1111 . 1111 1111 . 1000 0000 . 0000 0000 |
32,766 | |
| 18 | 255.255.192.0 | FF.FF.C0.00 | 1111 1111 . 1111 1111 . 1100 0000 . 0000 0000 |
16,382 | |
| 19 | 255.255.224.0 | FF.FF.E0.00 | 1111 1111 . 1111 1111 . 1110 0000 . 0000 0000 |
8190 | |
| 20 | 255.255.240.0 | FF.FF.F0.00 | 1111 1111 . 1111 1111 . 1111 0000 . 0000 0000 |
4094 | |
| 21 | 255.255.248.0 | FF.FF.F8.00 | 1111 1111 . 1111 1111 . 1111 1000 . 0000 0000 |
2046 | |
| 22 | 255.255.252.0 | FF.FF.FC.00 | 1111 1111 . 1111 1111 . 1111 1100 . 0000 0000 |
1022 | |
| 23 | 255.255.254.0 | FF.FF.FE.00 | 1111 1111 . 1111 1111 . 1111 1110 . 0000 0000 |
510 | |
| 24 | 255.255.255.0 | FF.FF.FF.00 | 1111 1111 . 1111 1111 . 1111 1111 . 0000 0000 |
254 | Class C |
| 25 | 255.255.255.128 | FF.FF.FF.80 | 1111 1111 . 1111 1111 . 1111 1111 . 1000 0000 |
126 | |
| 26 | 255.255.255.192 | FF.FF.FF.C0 | 1111 1111 . 1111 1111 . 1111 1111 . 1100 0000 |
62 | |
| 27 | 255.255.255.224 | FF.FF.FF.E0 | 1111 1111 . 1111 1111 . 1111 1111 . 1110 0000 |
30 | |
| 28 | 255.255.255.240 | FF.FF.FF.F0 | 1111 1111 . 1111 1111 . 1111 1111 . 1111 0000 |
14 | |
| 29 | 255.255.255.248 | FF.FF.FF.F8 | 1111 1111 . 1111 1111 . 1111 1111 . 1111 1000 |
6 | |
| 30 | 255.255.255.252 | FF.FF.FF.FC | 1111 1111 . 1111 1111 . 1111 1111 . 1111 1100 |
2 | |
| 31 | 255.255.255.254 | FF.FF.FF.FE | 1111 1111 . 1111 1111 . 1111 1111 . 1111 1110 |
0 | |
| 32 | 255.255.255.255 | FF.FF.FF.FF | 1111 1111 . 1111 1111 . 1111 1111 . 1111 1111 |
0 | |
- ↑ This is the number of usable host IP addresses. Note that total number of IP addresses for the subnet will be 2 more (network address and broadcast address). Its good practice to not have more than 254 hosts on a single broadcast domain/subnet.