How to calculate total number of usable host IDs on a network if subnet mask is given?
A host ID can be assigned to any device on a network.
How many host IDs can you use on a /24 network?
In binary, /24 is -
h = 2x - 2
where, h = no. of usable host IDs and x = no. of zeros in subnet mask.
We get, h = 28 - 2, as 254 usable host IDs.
What does “-2” signify? First of the total IDs is reserved for the “network ID” and the last ID is reserved for network broadcast ID.
This information will be used when we subnet a network.