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CIDR Calculator

Find host count and subnet mask from a CIDR prefix.

Calculated Output

Usable hosts 254

Subnet mask 255.255.255.0

Total addresses 256

Formula: addresses = 2^(32 - prefix); hosts = addresses - 2

Step-by-Step Breakdown

1. Values used:

2. Prefix length (/n) = 24

4. Usable hosts = 254

5. Subnet mask = 255.255.255.0

6. Total addresses = 256

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The math behind it

A /n prefix gives 2^(32-n) addresses; subtract 2 (network and broadcast) for usable hosts.

/24 gives 254 usable hosts and mask 255.255.255.0.

Why subtract 2?

The first address is the network ID and the last is the broadcast address.