1. What is CIDR Notation?

CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and its associated network mask. It specifies an IP address range by indicating the number of bits in the network prefix.

2. How Does the Calculator Work?

The calculator uses the following formula to convert CIDR to subnet mask:

Where:

• \( cidr \) — Number of bits in the network prefix (1-32)
• \( mask \) — Resulting subnet mask in IP address format

Explanation: The formula calculates the bitmask by creating a 32-bit number with the first 'cidr' bits set to 1 and the remaining bits set to 0.

3. Importance of CIDR Masks

Details: CIDR masks are essential for network configuration, routing, and defining IP address ranges. They allow for flexible allocation of IP addresses beyond traditional classful networks.

4. Using the Calculator

Tips: Enter the CIDR value (number of bits) between 1 and 32. The calculator will display the corresponding subnet mask in dotted-decimal notation.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between CIDR and subnet mask?
A: CIDR is a compact notation (e.g., /24) while subnet mask is the full representation (e.g., 255.255.255.0). They represent the same concept differently.

Q2: What are common CIDR values?
A: Common values include /24 (255.255.255.0), /16 (255.255.0.0), and /8 (255.0.0.0), but any value from 1-32 is valid.

Q3: How does CIDR relate to IP address ranges?
A: The CIDR value determines how many IP addresses are in a network. A /24 network has 256 addresses, /25 has 128, etc.

Q4: Can I use this for IPv6 addresses?
A: No, this calculator is for IPv4 only. IPv6 uses a similar concept but with 128-bit addresses.

Q5: Why would I need to calculate the mask?
A: Network administrators use masks to configure routers, firewalls, and to understand network boundaries and available host addresses.