Colin Robinson

Just another guy on the internet

IPv6 Subnet Calculator

I wrote a tool to organize subnet addressing for IPv6

Demo | Source Code

A little about IPv6


An IPv6 address is 128-bits and commonly represented as eight colon separated groups with each group consisting of four hexadecimal digits. For the general unicast address format, the first 64-bits are used for routing and the second 64-bits are the interface identifier (RFC 4291). Of the first 64-bits, the first 48 are used for regional routing and the next 16 are used for subnetting. Thus for practical subnet planning, you can assign blocks from /49 to /64. My calculator only lets you select a prefix up to /63 because if you can’t subnet a /64 block, you can only assign it.

How to use this calculator

Step 1)

You can enter the network IP to be subnetted as a full address or in the shortened form with leading zeros removed and consecutive groups of zeros removed.

Either 2001:09fe:000a:0000:0000:0000:0000:0000 or 2001:9fe:a:: is fine.

Step 2)

Enter the number of subnets you want created at each level and press “Add Level.” Example: your university has 10 colleges, each college has 3 buildings, and each building has 8 departments. Add 10, then 3, then 8.

Step 3)

Build it! Then use the + button to show / hide subnets. The position string on the left hand side should help you identify who the network is subnetted to (eg. the subnet in position 4.2.3 is the 3rd department in the second building of the 4th college).

Step 4)

Post questions in the comments and bugs on GitHub.

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