CIDR Calculator
Colorful, responsive IPv4 & IPv6 subnet calculator with live prefix sizing.
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📖 Understanding CIDR & IP Addresses
A quick guide to subnetting, CIDR blocks, and foundational internet protocols.
🌐
What is an IP Address?
An IP (Internet Protocol) address is a unique string of numbers separated by periods (or
colons) that identifies each computer running on a network. It acts much like a home address
for delivering mail, allowing data to be routed exactly where it needs to go across the
global internet.
4️⃣
IPv4 (Internet Protocol Version 4)
IPv4 is the older, incredibly common 32-bit address format consisting of four numbers from
0 to 255, such as
192.168.1.1. Due to its limited mathematical space (about 4.3
billion unique addresses), the world effectively ran out of standard IPv4 addresses,
accelerating the move to IPv6.
6️⃣
IPv6 (Internet Protocol Version 6)
IPv6 is the modern 128-bit upgrade created to solve the exhaustion of IPv4. It looks much
longer and incorporates hexadecimal letters, like
2001:0db8::8a2e:0370:7334.
IPv6 provides an essentially unlimited pool of unique addresses for modern devices.
🔪
What is CIDR?
CIDR (Classless Inter-Domain Routing) is a method used to efficiently assign and group IP
addresses. Instead of rigid old-school A/B/C classes, a CIDR notation appends a slash and a
number (like
/24) to an IP address. This single "block" cleanly represents an
entire range of connected IP addresses.
🧮
How is CIDR Calculated?
The number after the slash represents the "subnet mask." In an IPv4
/24
scenario, it means the first 24 bits of the 32-bit IP are fixed to describe the "Network,"
leaving the remaining 8 bits to identify individual "Hosts" (phones, laptops). 2 to the
power of those 8 remaining bits equals exactly 256 total IP addresses in that CIDR
block!