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Mame box

Here’s another project that’s been on the back burner for a while: my new Mame box:

This is the 5th arcade cabinet I turn into a Mame box. Gutting them always breaks my heart but having all the games in one cabinet with original artwork is very much worth it. The X-men cabinet is spacious, easy to work with and looks great.

The buttons and joysticks were bought from X-arcade: www.xgaming.com

And the control board to make them interface with a PC is an Ipac2: www.ultimarc.com

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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: