problem opening router port

hi, i am trying to setup my friends dbox500s for cardsharing. his setup is like this:

cable line-scientific atlanta 2100 modem-belkin n1 router-wireless laptop
-dreambox 500s

i am pretty sure the ports are open on the router (port 12000) but think they are being blocked by the modem as if i go on canyouseeme.com it says ports aren't open. i was wondering if anyone knew how to open the ports on the modem and if this would fix the problem. also would this allow incoming/outgoing connections. thanks in advance