CIDR

Here is a table of network masks:

    Short   Full                    Maximum         Comment
      Form    Form                    #Machines

    /8      /255.0.0.0              16,777,215      Used to be called an `A-class`
    /16     /255.255.0.0            65,535          Used to be called an `B-class`
    /17     /255.255.128.0          32,767
    /18     /255.255.192.0          16,383
    /19     /255.255.224.0          8,191
    /20     /255.255.240.0          4,095
    /21     /255.255.248.0          2,047
    /22     /255.255.252.0          1,023
    /23     /255.255.254.0          511
    /24     /255.255.255.0          255             Used to be called a `C-class`
    /25     /255.255.255.128        127
    /26     /255.255.255.192        63
    /27     /255.255.255.224        31
    /28     /255.255.255.240        15
    /29     /255.255.255.248        7
    /30     /255.255.255.252        3

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