Yeah, saw some old threads on this MAC issue in their forums. Have to try it out since I'm not sure if the commands remains relevant or not.
In any case, since I initially tied my MAC on Asus firmware to ViewQwest's ONT, there is no need to change anything in the official firmware.
I'm actually surprised no one here or rather not many people are aware that changing to DD-WRT will change the MAC. This has been a long outstanding issue.
In fact years ago, when change to DD-WRT, will have a default MAC of 00:11:22:33:44:55....