CIDR Conversion Table


CIDR Length Mask # Networks # Hosts
  /1 128.0.0.0 128 A     2,147,483,392  
  /2 192.0.0.0 64 A     1,073,741,696  
  /3 224.0.0.0 32 A     536,870,848  
  /4 240.0.0.0 16 A     268,435,424  
  /5 248.0.0.0 8 A     134,217,712  
  /6 252.0.0.0 4 A   67,108,856  
  /7 254.0.0.0 2 A   33,554,428  
  /8 255.0.0.0 1 A     16,777,214  
  /9 255.128.0.0 128 B   8,388,352  
  /10 255.192.0.0 64 B   4,194,176  
  /11 255.224.0.0 32 B   2,097,088  
  /12 255.240.0.0 16 B   1,048,544  
  /13 255.248.0.0 8 B   524,272  
  /14 255.252.0.0 4 B   262,136  
  /15 255.254.0.0 2 B   131,068  
  /16 255.255.0.0 1 B   65,024  
  /17 255.255.128.0 128 C   32,512  
  /18 255.255.192.0 64 C     16,256  
  /19 255.255.224.0 32 C     8,128  
  /20 255.255.240.0 16 C     4,064  
  /21 255.255.248.0 8 C     2,032  
  /22 255.255.252.0 4 C     1,016  
  /23 255.255.254.0 2 C     508  
  /24 255.255.255.0 1 C     254  
  /25 255.255.255.128   2 subnets   124  
  /26 255.255.255.192   4 subnets   62  
  /27 255.255.255.224   8 subnets   30  
  /28 255.255.255.240   16 subnets   14  
  /29 255.255.255.248 32 subnets   6  
  /30 255.255.255.252 64 subnets   2  
  /31   255.255.255.254     none   none
  /32 255.255.255.255   1/256 C 1  

  

A network is called a supernet when the prefix boundary contains fewer bits than the network's natural (i.e. classful) mask. A network is called a subnet when the prefix boundary contains more bits than the network's natural mask.

Examples

209.60.128.0 is a class C network address with a natural mask of /24.

209.60.128.0 /22 is a supernet which yields:

209.60.128.0 /24
209.60.129.0 /24
209.60.130.0 /24
209.60.131.0 /24

192.0.0.0 /25
Subnet    Host Range
  0        192.0.0.1      -  192.0.0.126
  1        192.0.0.129  -  192.0.0.254

192.0.0.0 /26
Subnet Host Range
0 192.0.0.1 - 192.0.0.62
1 192.0.0.65 - 192.0.0.126
2 192.0.0.129 - 192.0.0.190
3 192.0.0.193 - 192.0.0.254

192.0.0.0 /27
Subnet Host Range
0 192.0.0.1 - 192.0.0.30
1 192.0.0.33 - 192.0.0.62
2 192.0.0.65 - 192.0.0.94
3 192.0.0.97 - 192.0.0.126
4 192.0.0.129 - 192.0.0.158
5 192.0.0.161 - 192.0.0.190
6 192.0.0.193 - 192.0.0.222
7 192.0.0.225 - 192.0.0.254

  

Reserved Network Numbers


Class Start End # Hosts Comment
  A   10.0.0.0   10.255.255.255   16,777,216   a single Class A network number
  B   172.16.0.0   172.31.255.255 1,048,544   16 contiguous Class B network numbers
  C   192.168.0.0     192.168.255.255   65,534   256 contiguous Class C network numbers  


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Creation Date: Saturday, October 19, 1996
Last Modified: Saturday, November 30, 1996
Copyright © Ray Smith, 1996