mt-daapd behind NAT

At school, I’m only allowed one IP to use for my computers. So to remedy this problem, I got a Linksys WRT54GS, I’m running dd-wrt on it so I have control over iptables and such. I was wondering if it’s possible to share my music with my roommate. My computers that i have are all 192.168.1.* but my wan ip is 10.20.11.89 (example) and my roommate is 10.20.11.132. I’m not entirely sure that it’s possible, because i remember hearing something about only routing over local subnet. but does anyone know how, if it’s possible, to share it over the wan?