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Glossary - Network mask
The "network mask" (or "netmask" or simply "mask") is a value that defines the subnet of an IPv4 address. It accounts for all 32-bits of the IP address at the bit-level by splitting it into "networks" and "hosts" portions.
Usually the mask is expressed with the IP address either in CIDR notation (where the number of bits in the mask that identifies the "networks" portion is preceeded by a slash), or separately in the same format as the IPv4 address itself (often referred to as "dotted-decimal").
Reference chart
CIDR/bits |
Dotted-decimal |
Hexadecimal |
Binary |
Hosts |
/0 |
0.0.0.0 |
00 00 00 00 |
00000000 00000000 00000000 00000000 |
4,294,967,296 |
/1 |
128.0.0.0 |
80 00 00 00 |
10000000 00000000 00000000 00000000 |
2,147,483,648 |
/2 |
192.0.0.0 |
c0 00 00 00 |
11000000 00000000 00000000 00000000 |
1,073,741,824 |
/3 |
224.0.0.0 |
e0 00 00 00 |
11100000 00000000 00000000 00000000 |
536,870,912 |
/4 |
240.0.0.0 |
f0 00 00 00 |
11110000 00000000 00000000 00000000 |
268,435,456 |
/5 |
248.0.0.0 |
f8 00 00 00 |
11111000 00000000 00000000 00000000 |
134,217,728 |
/6 |
252.0.0.0 |
fc 00 00 00 |
11111100 00000000 00000000 00000000 |
67,108,864 |
/7 |
254.0.0.0 |
fe 00 00 00 |
11111110 00000000 00000000 00000000 |
33,554,432 |
/8 |
255.0.0.0 |
ff 00 00 00 |
11111111 00000000 00000000 00000000 |
16,777,216 |
CIDR/bits |
Dotted-decimal |
Hexadecimal |
Binary |
Hosts |
/9 |
255.128.0.0 |
ff 80 00 00 |
11111111 10000000 00000000 00000000 |
8,388,608 |
/10 |
255.192.0.0 |
ff c0 00 00 |
11111111 11000000 00000000 00000000 |
4,194,304 |
/11 |
255.224.0.0 |
ff e0 00 00 |
11111111 11100000 00000000 00000000 |
2,097,152 |
/12 |
255.240.0.0 |
ff f0 00 00 |
11111111 11110000 00000000 00000000 |
1,048,576 |
/13 |
255.248.0.0 |
ff f8 00 00 |
11111111 11111000 00000000 00000000 |
524,288 |
/14 |
255.252.0.0 |
ff fc 00 00 |
11111111 11111100 00000000 00000000 |
262,144 |
/15 |
255.254.0.0 |
ff fe 00 00 |
11111111 11111110 00000000 00000000 |
131,072 |
/16 |
255.255.0.0 |
ff ff 00 00 |
11111111 11111111 00000000 00000000 |
65,536 |
CIDR/bits |
Dotted-decimal |
Hexadecimal |
Binary |
Hosts |
/17 |
255.255.128.0 |
ff ff 80 00 |
11111111 11111111 10000000 00000000 |
32,768 |
/18 |
255.255.192.0 |
ff ff c0 00 |
11111111 11111111 11000000 00000000 |
16,384 |
/19 |
255.255.224.0 |
ff ff e0 00 |
11111111 11111111 11100000 00000000 |
8,192 |
/20 |
255.255.240.0 |
ff ff f0 00 |
11111111 11111111 11110000 00000000 |
4,096 |
/21 |
255.255.248.0 |
ff ff f8 00 |
11111111 11111111 11111000 00000000 |
2,048 |
/22 |
255.255.252.0 |
ff ff fc 00 |
11111111 11111111 11111100 00000000 |
1,024 |
/23 |
255.255.254.0 |
ff ff fe 00 |
11111111 11111111 11111110 00000000 |
512 |
/24 |
255.255.255.0 |
ff ff ff 00 |
11111111 11111111 11111111 00000000 |
256 |
CIDR/bits |
Dotted-decimal |
Hexadecimal |
Binary |
Hosts |
/25 |
255.255.255.128 |
ff ff ff 80 |
11111111 11111111 11111111 10000000 |
128 |
/26 |
255.255.255.192 |
ff ff ff c0 |
11111111 11111111 11111111 11000000 |
64 |
/27 |
255.255.255.224 |
ff ff ff e0 |
11111111 11111111 11111111 11100000 |
32 |
/28 |
255.255.255.240 |
ff ff ff f0 |
11111111 11111111 11111111 11110000 |
16 |
/29 |
255.255.255.248 |
ff ff ff f8 |
11111111 11111111 11111111 11111000 |
8 |
/30 |
255.255.255.252 |
ff ff ff fc |
11111111 11111111 11111111 11111100 |
4 |
/31 |
255.255.255.254 |
ff ff ff fe |
11111111 11111111 11111111 11111110 |
2 |
/32 |
255.255.255.255 |
ff ff ff ff |
11111111 11111111 11111111 11111111 |
1 |
CIDR/bits |
Dotted-decimal |
Hexadecimal |
Binary |
Hosts |
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