Subnet mask cheat sheet, which shows the common subnet masks and their corresponding CIDR (Classless Inter-Domain Routing) notations:
|
CIDR Notation |
Subnet Mask |
Number of IPs |
Usable IPs |
Description |
|
/32 |
255.255.255.255 |
1 |
1 |
Single Host |
|
/31 |
255.255.255.254 |
2 |
0 |
Point-to-Point Link |
|
/30 |
255.255.255.252 |
4 |
2 |
Very Small Subnet |
|
/29 |
255.255.255.248 |
8 |
6 |
Small Subnet |
|
/28 |
255.255.255.240 |
16 |
14 |
Small Subnet |
|
/27 |
255.255.255.224 |
32 |
30 |
Small Subnet |
|
/26 |
255.255.255.192 |
64 |
62 |
Medium Subnet |
|
/25 |
255.255.255.128 |
128 |
126 |
Medium Subnet |
|
/24 |
255.255.255.0 |
256 |
254 |
Large Subnet |
|
/23 |
255.255.254.0 |
512 |
510 |
Large Subnet |
|
/22 |
255.255.252.0 |
1,024 |
1,022 |
Large Subnet |
|
/21 |
255.255.248.0 |
2,048 |
2,046 |
Large Subnet |
|
/20 |
255.255.240.0 |
4,096 |
4,094 |
Large Subnet |
|
/19 |
255.255.224.0 |
8,192 |
8,190 |
Large Subnet |
|
/18 |
255.255.192.0 |
16,384 |
16,382 |
Large Subnet |
|
/17 |
255.255.128.0 |
32,768 |
32,766 |
Large Subnet |
|
/16 |
255.255.0.0 |
65,536 |
65,534 |
Very Large Subnet |
|
/15 |
255.254.0.0 |
131,072 |
131,070 |
Very Large Subnet |
|
/14 |
255.252.0.0 |
262,144 |
262,142 |
Very Large Subnet |
|
/13 |
255.248.0.0 |
524,288 |
524,286 |
Very Large Subnet |
|
/12 |
255.240.0.0 |
1,048,576 |
1,048,574 |
Very Large Subnet |
|
/11 |
255.224.0.0 |
2,097,152 |
2,097,150 |
Very Large Subnet |
|
/10 |
255.192.0.0 |
4,194,304 |
4,194,302 |
Very Large Subnet |
|
/9 |
255.128.0.0 |
8,388,608 |
8,388,606 |
Very Large Subnet |
|
/8 |
255.0.0.0 |
16,777,216 |
16,777,214 |
Class A Subnet |
Note: The number of usable IPs excludes the network and broadcast addresses, which cannot be assigned to hosts. The network address represents the beginning of the subnet range, and the broadcast address represents the end of the subnet range.