1. What is IPv6 CIDR?

CIDR (Classless Inter-Domain Routing) notation is a method for allocating IP addresses and routing Internet Protocol packets. For IPv6, it specifies the network portion of the address with a prefix length (e.g., /64).

2. How Does the Calculator Work?

The calculator uses the IPv6 CIDR formula:

Where:

• \( \text{Prefix} \) — The network prefix length (0-128 bits)
• \( 128 \) — Total bits in an IPv6 address

Explanation: The formula calculates the number of possible host addresses by raising 2 to the power of the remaining bits after the prefix.

3. Importance of CIDR Notation

Details: CIDR notation is essential for efficient IP address allocation, subnetting, and routing in IPv6 networks. It helps prevent address exhaustion and enables hierarchical routing.

4. Using the Calculator

Tips: Enter the prefix length (typically between 32 and 128 for IPv6). Common prefixes include /64 (standard subnet size) and /48 (typical allocation for sites).

5. Frequently Asked Questions (FAQ)

Q1: What's a typical IPv6 prefix length?
A: /64 is standard for most subnets, while /48 is commonly allocated to sites. /128 is a single host address.

Q2: Why does IPv6 have so many addresses?
A: IPv6's 128-bit address space provides approximately 3.4×10³⁸ addresses to ensure no future exhaustion.

Q3: What's the smallest possible subnet in IPv6?
A: Technically /127 (for point-to-point links), though /64 is recommended for most cases.

Q4: How does this compare to IPv4 CIDR?
A: IPv4 uses 32-bit addresses, so its formula is 2^(32-prefix). IPv6's larger space allows simpler allocation schemes.

Q5: What prefix should I use for my network?
A: Follow your ISP's allocation, but /64 is standard for LANs, while /56 or /48 may be used for larger networks.