If you happen to be in Berlin, you can get <a href="https://www.hotspot.kabeldeutschland.de/" target="_blank">30 minutes of free WiFi</a> in quite a lot of places from a KabelDeutschland™ HotSpot. Unfortunately, each connecting device gets only 30 minutes of free internet per day. On a completely unrelated note, I will talk about changing the MAC address of your WiFi card in Windows 7. I must, again, emphasize the fact that these two topics are in no way related. <span id="more-2086"></span>
# How to change the MAC
* Do an `ipconfig /all` and find the description of your WiFi card's adapter.
* Go to `HKEY_LOCAL_MACHINE` → `\SYSTEM` → `\CurrentControlSet` → `\Control` → `\Class` → `\{4D36E972-E325-11CE-BFC1-08002BE10318}` as an administrator and navigate to the subkey whose `DriverDesc` matches this description.
* Change the entry `NetworkAddress` to the desired MAC address. It's supposed to be a string value of exactly 12 hexadecimal digits, no spaces or dashes. If the key does not exist, simply create it.
* Disable and re-enable your network adapter.
Alternatively, you can download <a href="http://www.codeproject.com/Articles/10493/MAC-Address-Changer-for-Windows-XP-2003" target="_blank">the MAC Address Changer</a> from <a href="http://www.codeproject.com" target="_blank">CodeProject</a>, which is open source and performs <i>exactly</i> the above procedure, but with a nice GUI.
# That all?
No. Of course not. I was changing my MAC back and forth and the adapter just kept switching back to the original MAC, until I finally figured out the problem. In Windows 7, if the MAC of a WiFi adapter is of the form `XY-XX-XX-XX-XX-XX`, then `X` may be any hexadecimal digit. However, the lower two bits of `Y` have a special meaning. Write `Y=[abcd]`, i.e. `a` to `d` are the binary digits of `Y`. Then,
\[
d = \left\{ \begin{array}{ccl}
0 &;& \text{Unicast} \\
1 &;& \text{Multicast}
\end{array}\right.
\qquad
c = \left\{ \begin{array}{ccl}
0 &;& \text{globally assigned MAC} \\
1 &;& \text{locally administered}
\end{array}\right.
\]
We want our adapter to be unicast and locally administered. So we're left with the four choices `2`, `6`, `A` and `E` for `Y`.
# So now that's all?
Yea that's all. Enjoy Berlin!
One Reply to “Kabel Deutschland HotSpots and WiFi MAC’s”