using "reserved" IPv6 space

Jeroen Massar jeroen at
Tue Jul 17 22:34:37 UTC 2012

On 2012-07-18 00:21, Seth Mattinen wrote:
> Don't, because there's already a /10 defined for such things. It's
> called ULA (unique local address) aka RFC 4193. ULAs are not globally
> routable.
> Here's a calculator that will generate a random one for you:

A random one indeed, because the javascript for it is just:
  var calc_private = function() {

    var str = "fd";

    for(i = 0; i<10; i++) {
      str = str + toHex(Math.floor(Math.random()*16));
      if (i % 4 == 1) str = str + ":";

    $("#private_subnet").html("Your private subnet is:

does not follow RFC4193 in any way at all. A such do not use it.

The original real RFC4193 ULA generator script can be found at:

google(ipv6 ula) for another page, that has been referenced often enough
on this very list already, if you want to 'register' it there to avoid
another small chance of collision, that page also uses the script from
the above site for a true RFC4193 prefix.


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