This IPv6 nibble boundary planner helps you split an IPv6 allocation into sites and LANs on 4-bit boundaries and shows the reverse DNS zones each level needs. It runs entirely in your browser: nothing you type is sent to our server.
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Table of Contents
Why plan on nibble boundaries
Each hex digit in an IPv6 address is 4 bits (a nibble). Subnetting on multiples of 4 (/48, /52, /56, /60, /64) means each level changes whole hex digits, so addresses are easy to read and every subnet has its own ip6.arpa reverse zone. A /29 allocation, which is not a multiple of 4, needs 8 separate /32 reverse zones.
A typical plan
| Level | Prefix | Count |
|---|---|---|
| ISP or LIR allocation | /32 | 1 |
| Region or POP | /36 or /40 | 16 or 256 per /32 |
| Customer site | /48 | 65,536 per /32 |
| Home or small site | /56 | 256 per /48 |
| LAN / VLAN | /64 | 256 per /56 |
Use /64 for every LAN: SLAAC and many IPv6 features require it. For details of one block, use the IPv6 subnet calculator.
How we checked it
We checked subnet counts and the zone split for a /29 against Python’s ipaddress module, and verified the ip6.arpa names digit by digit.
Frequently asked questions
What is an IPv6 nibble boundary?
A prefix length that is a multiple of 4, so it ends at a whole hex digit: /48, /52, /56, /60, /64.
How many /64 networks are in a /48?
65,536.
What is the reverse DNS zone for 2001:db8::/32?
8.b.d.0.1.0.0.2.ip6.arpa: the first 8 hex digits, reversed and separated by dots.