Changing MAC Address

So here is my concern, i followed this procedure :

Check my IP : sudo ifconfig
Create a random IP : openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/.$//'
Then : sudo /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -z
Add new IP : sudo ifconfig en0 ether (new IP)
Then double check : ifconfig en0 |grep ether or sudo ifconfig

After that everything seems good, the new ip will appear with either "ifconfig en0 |grep ether" or "sudo ifconfig" command, but if i go to System preferences > Network > Advanced.. the real mac address will still show up!! is that normal?



2nd question : Do i need to spoof my mac address while using a 3g USB key or the USB key will show its own mac?

 

I just want to spoof my mac address and be sure it worked with the procedure i used above!

For the second part, my question was do i still need to spoof my mac address when using a 3G key? i read some things saying the 3g key or any device like that have their own mac address and it's this one who would be seen by the internet provider and not the one from my mac!

I just to want to have your confirmation

 

Thanks Weaselboy

and any idea why i can still see the original Mac address in the Preferences/Network after having successfully spoofed it in the terminal

 

Thanks

I thought it could be something like that..