the first 3 sets of digits has to be as below..
00:1A:78
Then you would add the next 3 sets of digits.
Use an online MAC generator to get a MAC addy that will work.
The generator tool linked below will allow you to set them first 3 sets of digits, then it will generate the next 3 sets for you
Code:
http://www.miniwebtool.com/mac-address-generator/