MAC address to IPv6 link-local address online converter

The converter

It can also be addressed directly via:
https://ben.akrin.com/ipv6_mac_address_to_link_local_converter/?mode=api&mac=52:74:f2:b1:a8:7f
for all your API needs.

The math

Link-local IPv6 addresses are used as part of the IPv6 network auto-configuration process. Instead of getting an address via DHCP, a NIC will hop on the network with a link-local IPv6 address and with this will have to ability to do further configuration automatically (soliciting neighbors, router, et cetera).

This link-local IPv6 is infered from the NIC’s mac address.

A mac address is 48 bits, an IPv6 address is 128 bits. Here’s the conversion process step by step:

  1. take the mac address: for example 52:74:f2:b1:a8:7f
  2. throw ff:fe in the middle: 52:74:f2:ff:fe:b1:a8:7f
  3. reformat to IPv6 notation 5274:f2ff:feb1:a87f
  4. convert the first octet from hexadecimal to binary: 52 -> 01010010
  5. invert the bit at index 6 (counting from 0): 01010010 -> 01010000
  6. convert octet back to hexadecimal: 01010000 -> 50
  7. replace first octet with newly calculated one: 5074:f2ff:feb1:a87f
  8. prepend the link-local prefix: fe80::5074:f2ff:feb1:a87f
  9. done!

Going the other way

A converter to do the same operation in reverse is available here.

Comments

There have been a few interesting comments on this post, I encourage you to read them if you want to learn more about this mechanism. Specifically:

Top-bar beehive design

Here’s a Google Sketchup design for a simple top-bar beehive.

Some pics:


Notes:

Only 2 measurements really matter in the design of a top-bar beehive: the angle of the side panels (70 degrees) & the width of the top bars 35mm. They both pertain to bee behavior and this design has them both optimized. From what I gather, other measures are quite forgiving.

This design is simple & well researched, I do not know yet how it will fare in practice, more to come on that.

Material:

All you’ll need as far as wood is concerned is a couple of 2x12x16 and a 3/4″ sheet of plywood:

Lastly, all units are in millimeters but based on standard lumber sizes available at the hardware store.