If an organization has lots of computers, or if its computers are geographically spread, it’s a good idea to divide its netwerk into smaller ones (subnets) connected by routers. The benefit of using subnets are less traffic (most traffic will stay on the local netwerk) and easier to isolate and identify a network problem.
The subnet mask splits an IPv4 address into a network and a host portion.
In this table below you can see how you can split your subnets using a subnet mask.
| binary subnet mask | decimal subnet mask | Mask Bits | nodes per subnet |
| 1 | 0.0.0.0 | /1 | 2147483648 |
| 11 | 128.0.0.0 | /2 | 1073741824 |
| 111 | 192.0.0.0 | /3 | 536870912 |
| 1111 | 224.0.0.0 | /4 | 268435456 |
| 1111.1 | 248.0.0.0 | /5 | 134217728 |
| 1111.11 | 252.0.0.0 | /6 | 67108864 |
| 1111.111 | 254.0.0.0 | /7 | 33554432 |
| CLASS A | |||
| 1111.1111 | 255.0.0.0 | /8 | 16777214 |
| 1111.1111 1 | 255.128.0.0 | /9 | 8388606 |
| 1111.1111 11 | 255.192.0.0 | /10 | 4194302 |
| 1111.1111 111 | 255.224.0.0 | /11 | 2097150 |
| 1111.1111 1111. | 255.240.0.0 | /12 | 1048574 |
| 1111.1111 1111.1 | 255.248.0.0 | /13 | 524286 |
| 1111.1111 1111.11 | 255.252.0.0 | /14 | 262142 |
| 1111.1111 1111.111 | 255.254.0.0 | /15 | 131070 |
| CLASS B | |||
| 1111.1111 1111.1111 | 255.255.0.0 | /16 | 65534 |
| 1111.1111 1111.1111 1 | 255.255.128.0 | /17 | 32766 |
| 1111.1111 1111.1111 11 | 255.255.192.0 | /18 | 16382 |
| 1111.1111 1111.1111 111 | 255.255.224.0 | /19 | 8190 |
| 1111.1111 1111.1111 1111 | 255.255.240.0 | /20 | 4094 |
| 1111.1111 1111.1111 1111.1 | 255.255.248.0 | /21 | 2046 |
| 1111.1111 1111.1111 1111.11 | 255.255.252.0 | /22 | 1022 |
| 1111.1111 1111.1111 1111.111 | 255.255.254.0 | /23 | 510 |
| CLASS C | |||
| 1111.1111 1111.1111 1111.1111 | 255.255.255.0 | /24 | 254 |
| 1111.1111 1111.1111 1111.1111 1 | 255.255.255.128 | /25 | 126 |
| 1111.1111 1111.1111 1111.1111 11 | 255.255.255.192 | /26 | 62 |
| 1111.1111 1111.1111 1111.1111 111 | 255.255.255.224 | /27 | 30 |
| 1111.1111 1111.1111 1111.1111 1111 | 255.255.255.240 | /28 | 14 |
| 1111.1111 1111.1111 1111.1111 1111.1 | 255.255.255.248 | /29 | 6 |
| 1111.1111 1111.1111 1111.1111 1111.11 | 255.255.255.252 | /30 | 2 |
| 1111.1111 1111.1111 1111.1111 1111.111 | 255.255.255.254 | /31 | 0 |
| 1111.1111 1111.1111 1111.1111 1111.1111 | 255.255.255.255 | /32 | 0 |
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