Understanding Subnetting
To use these tables, there are a few things you need to understand.
- First, the "Extra Newtork Bits" is the number of bits being borrowed form the host bits beyond the classful boundry.
- Second, the "Increment" is the value you add to one network ID to get to the next one. Take note of which octet you are in
Class C: 24 Network Bits
| Extra Network Bits |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
| # Subnets |
1 |
2 |
4 |
8 |
16 |
32 |
64 |
128 |
256 |
| # Hosts/Sub |
254 |
126 |
62 |
30 |
14 |
6 |
2 |
0 |
|
| Subnet Mask |
255.255.255.0 |
255.255.255.128 |
255.255.255.192 |
255.255.255.224 |
255.255.255.240 |
255.255.255.248 |
255.255.255.252 |
255.255.255.254 |
255.255.255.255 |
| CIDR |
/24 |
/25 |
/26 |
/27 |
/28 |
/29 |
/30 |
/31 |
/32 |
| Increment |
0.0.1.0 |
0.0.0.128 |
0.0.0.64 |
0.0.0.32 |
0.0.0.16 |
0.0.0.8 |
0.0.0.4 |
0.0.0.2 |
0.0.0.1 |
Class B: 16 Network Bits
| Extra Network Bits |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
| # Subnets |
1 |
2 |
4 |
8 |
16 |
32 |
64 |
128 |
256 |
512 |
1024 |
2048 |
4096 |
8192 |
16384 |
32768 |
65536 |
| # Hosts/Sub |
65534 |
32766 |
16382 |
8190 |
4094 |
2046 |
1022 |
510 |
254 |
126 |
62 |
30 |
14 |
6 |
2 |
0 |
|
| Subnet Mask |
255.255.0.0 |
255.255.128.0 |
255.255.192.0 |
255.255.224.0 |
255.255.240.0 |
255.255.248.0 |
255.255.252.0 |
255.255.254.0 |
255.255.255.0 |
255.255.255.128 |
255.255.255.192 |
255.255.255.224 |
255.255.255.240 |
255.255.255.248 |
255.255.255.252 |
255.255.255.254 |
255.255.255.255 |
| CIDR |
/16 |
/17 |
/18 |
/19 |
/20 |
/21 |
/22 |
/23 |
/24 |
/25 |
/26 |
/27 |
/28 |
/29 |
/30 |
/31 |
/32 |
| Increment |
0.1.0.0 |
0.0.128.0 |
0.0.64.0 |
0.0.32.0 |
0.0.16.0 |
0.0.8.0 |
0.0.4.0 |
0.0.2.0 |
0.0.1.0 |
0.0.0.128 |
0.0.0.64 |
0.0.0.32 |
0.0.0.16 |
0.0.0.8 |
0.0.0.4 |
0.0.0.2 |
0.0.0.1 |
Class A : 8 Network Bits
| Extra Network Bits |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
| # Subnets |
1 |
2 |
4 |
8 |
16 |
32 |
64 |
128 |
256 |
512 |
1024 |
2048 |
4096 |
8192 |
16384 |
32768 |
65536 |
131072 |
262144 |
524288 |
1048576 |
2097152 |
4194304 |
8388608 |
16777216 |
| # Hosts/Sub |
16777212 |
8388606 |
4194302 |
2097150 |
1048574 |
524286 |
262142 |
131070 |
65534 |
32766 |
16382 |
8190 |
4094 |
2046 |
1022 |
510 |
254 |
126 |
62 |
30 |
14 |
6 |
2 |
0 |
|
| Subnet Mask |
255.0.0.0 |
255.128.0.0 |
255.192.0.0 |
255.224.0.0 |
255.240.0.0 |
255.248.0.0 |
255.252.0.0 |
255.254.0.0 |
255.255.0.0 |
255.255.128.0 |
255.255.192.0 |
255.255.224.0 |
255.255.240.0 |
255.255.248.0 |
255.255.252.0 |
255.255.254.0 |
255.255.255.0 |
255.255.255.128 |
255.255.255.192 |
255.255.255.224 |
255.255.255.240 |
255.255.255.248 |
255.255.255.252 |
255.255.255.254 |
255.255.255.255 |
| CIDR |
/8 |
/9 |
/10 |
/11 |
/12 |
/13 |
/14 |
/15 |
/16 |
/17 |
/18 |
/19 |
/20 |
/21 |
/22 |
/23 |
/24 |
/25 |
/26 |
/27 |
/28 |
/29 |
/30 |
/31 |
/32 |
| Increment |
1.0.0.0 |
0.128.0.0 |
0.64.0.0 |
0.32.0.0 |
0.16.0.0 |
0.8.0.0 |
0.4.0.0 |
0.2.0.0 |
0.1.0.0 |
0.0.128.0 |
0.0.64.0 |
0.0.32.0 |
0.0.16.0 |
0.0.8.0 |
0.0.4.0 |
0.0.2.0 |
0.0.1.0 |
0.0.0.128 |
0.0.0.64 |
0.0.0.32 |
0.0.0.16 |
0.0.0.8 |
0.0.0.4 |
0.0.0.2 |
0.0.0.1 |