just did a little google and found this from another forum...
"The MAC address of your PC or your router doesn't matter in the slightest. Most routers even allow you to change your MAC via their GUI. Your MAC address however is not going to make it past the first hop on the way to battle.net because they are local to the subnet they're on. So it is an ultimate exercise in futility to change it."
"Quote:
Originally Posted by barker 
The point is to get a new IP from your ISP after changing your MAC address. Not all ISP's allow simply /release /renew, so in order to get a new IP address, you need to change the router's MAC. At least it's the only way I can get a new IP on my service provider, it works every time. New IP = Bypassing the ban = non-futile exercise :wink3:
You still shouldn't have to change your mac address if you release your IP before renewing. Unless your ISP is doing something funky (which is possible), it should give you a new one out of the DHCP pool.
It will likely be different with every ISP. My point is that it's not the MAC address that matters with regard to your battle.net connection, it's your IP."
check this out as well...
Ok, but what if something else goes wrong and you get it anyways, what do you do? A while back we experimented with using various IP spoofers to see which worked the best. Through this a half decent program was found:
http://www.klcconsulting.net/smac/
The full thing is not free but there is a usable version of it to suit our needs. This program can fool your
computer into thinking you have a different
MAC address then you actually do, thus changing your
IP address. Some of this is dependent on your ISP and how it works. Because even if you change your Mac address the first three sets of your IP will always be the same. (IP: same.same.same.new). So say your IP is 185.12.21.79. After changing your
MAC address and rebooting quickly (hey its better then waiting 30 min or usually longer for realms to go back up) your IP might look something like this: 185.12.21.103. Like I said this is completely dependent on how your ISP works. Also note that you cant do this through a router because a router has its own MAC address as well which is seen before the one you set on the computer. If this is the case you don't even need to use this program. Simply don't use your router for a while because by plugging directly into the wall, your new IP will be based off the MAC address of your computers vs the routers.
Remember if you do get a Realm down error, don't repeatedly login because it appears that when you do this, the amount of time it takes to go away tends to stack or even multiply in extreme cases. If you're not going use the above method or if you do and it still fails you'll want to leave the game alone for at least an hour to be safe that when you log back in you wont get it again. If you log in and still see it you may want to wait an additional 2-3 hours.
Hope this helps some of you get playing again. The program is simple and easy to use but if you need help you can post in the forums:
http://virtualfragment.net. And of course if anyone knows of another good IP spoofing program post any info there as well.
also check this out to see if it helps...
http://compnetworking.about.com/od/networkprotocolsip/a/macaddressing_2.htm
sorry i don't have any definitive answer.
perhaps the info above might get you closer to your answer.
