1. What is CIDR Notation?

CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and its associated routing prefix. It's written as an IP address followed by a slash and the prefix length (e.g., 192.168.1.0/24).

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( cidr \) — The number of bits in the network prefix (1-32)
• \( hosts \) — The number of available host addresses

Explanation: The formula calculates the number of available IP addresses by taking the remaining bits after the network prefix and subtracting 2 (for network and broadcast addresses).

3. Importance of CIDR Calculation

Details: Understanding CIDR notation and host calculations is essential for network design, subnetting, and efficient IP address allocation.

4. Using the Calculator

Tips: Enter the CIDR prefix length (1-32) to calculate the number of available hosts in that subnet. The calculator automatically computes the result.

5. Frequently Asked Questions (FAQ)

Q1: Why subtract 2 from the host count?
A: In any subnet, two addresses are reserved - the network address (all host bits 0) and the broadcast address (all host bits 1).

Q2: What's the maximum number of hosts possible?
A: The maximum is 2³²-2 = 4,294,967,294 hosts (for CIDR /0), but in practice, the largest commonly used is /8 with 16,777,214 hosts.

Q3: What CIDR gives exactly 254 hosts?
A: CIDR /24 (255.255.255.0) provides 254 hosts, commonly used in small networks.

Q4: Are there exceptions to the -2 rule?
A: Yes, point-to-point links (/31) and /32 addresses don't follow this rule and have special handling.

Q5: How does IPv6 CIDR calculation differ?
A: IPv6 uses 128-bit addresses, so the formula becomes 2^(128 - cidr), and typically doesn't subtract 2.