What does the "/24" mean? How does that relate to my subnet mask?
InterMapper uses the Classless Inter-Domain Routing (CIDR) notation to represent IP subnet information. The number in the "/xx" shorthand stands for the number of bits set to one in the subnet mask. The convention is always to start at the left end of the 32-bit subnet mask. The table below shows the correspondence between the "/xx" notation and the actual numeric representation.
| |
Subnet Mask |
# of Addresses |
|
Subnet Mask |
# of Addresses |
| /1 |
128.0.0.0 |
2.1 billion |
/17 |
255.255.128.0 |
32,766 |
| /2 |
192.0.0.0 |
1 billion |
/18 |
255.255.192.0 |
16,382 |
| /3 |
224.0.0.0 |
536 million |
/19 |
255.255.224.0 |
8,190 |
| /4 |
240.0.0.0 |
268 million |
/20 |
255.255.240.0 |
4,094 |
| /5 |
248.0.0.0 |
134 million |
/21 |
255.255.248.0 |
2,046 |
| /6 |
252.0.0.0 |
67 million |
/22 |
255.255.252.0 |
1,022 |
| /7 |
254.0.0.0 |
34 million |
/23 |
255.255.254.0 |
510 |
| /8 |
255.0.0.0 |
17 million (Class A) |
/24 |
255.255.255.0 |
254 (Class C) |
| /9 |
255.128.0.0 |
8.4 million |
/25 |
255.255.255.128 |
126 |
| /10 |
255.192.0.0 |
4.2 million |
/26 |
255.255.255.192 |
62 |
| /11 |
255.224.0.0 |
2.1 million |
/27 |
255.255.255.224 |
30 |
| /12 |
255.240.0.0 |
1 million |
/28 |
255.255.255.240 |
14 |
| /13 |
255.248.0.0 |
524 thousand |
/29 |
255.255.255.248 |
6 |
| /14 |
255.252.0.0 |
262 thousand |
/30 |
255.255.255.252 |
2 |
| /15 |
255.254.0.0 |
131 thousand |
/31 |
255.255.255.254 |
RFC 3021 |
| /16 |
255.255.0.0 |
65,534 (Class B) |
/32 |
255.255.255.255. |
A single address |
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