Question 1

What is CIDR notation?

Accepted Answer

CIDR (Classless Inter-Domain Routing) notation represents an IP address and its subnet mask in the format IP/prefix (e.g. 192.168.1.0/24). The prefix number indicates how many bits are used for the network portion, determining the size of the subnet.

Question 2

How many usable hosts does a /24 subnet have?

Accepted Answer

A /24 subnet has 254 usable host addresses (256 total minus the network address and broadcast address). Common subnet sizes: /24 = 254 hosts, /16 = 65,534 hosts, /8 = 16,777,214 hosts.

Question 3

What is the difference between CIDR and subnet calculator?

Accepted Answer

They calculate the same information from different inputs. A CIDR calculator takes slash notation (e.g. /24) while a subnet calculator takes the full mask (e.g. 255.255.255.0). HackMyIP offers both tools for convenience.

CIDR / IP Range Calculator