Mask

A better way to define a block of addresses is to select any address in the block and the

mask. As we discussed before, a mask is a 32-bit number in which the n leftmost bits

are Is and the 32 - n rightmost bits are Os. However, in classless addressing the mask

for a block can take any value from 0 to 32. It is very convenient to give just the value

of n preceded by a slash (CIDR notation).


In 1Pv4 addressing, a block of addresses can be defined as

x.y.z.tln


in which x.y.z.t defines one of the addresses and the In defines the mask.

The address and the In notation completely define the whole block (the first

address, the last address, and the number of addresses).


First Address The first address in the block can be found by setting the 32 - n right-

most bits in the binary notation of the address to Os.


여기서 A better way to define a block of addresses is to select any address in the block and the

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