I don't have access to a Gentoo box atm. But there is an option in /etc/conf.d/net for this.
Check the net.example file.

--
Joost

Joseph <syscon780@gmail.com> wrote:
>Does anybody know how to spoof mac address on Gentoo?
>
>I want to connect a machine directly to the modem but if I do so my
>static IP will change; so to retain static IP I want to spoof mac
>address on one of my machine to 
>the same MAC as on my router.
>
>-- 
>Joseph

-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.