Have a look here lets you know about the WAN to LAN and the LAN to WAN plus some other bits and bobs
http://www.smallnetbuilder.com/compo...rt/Itemid,189/
EDIT
I will also help if look at a bit of future proofing as speeds get quicker you will want something that will last as with 50Mb and 100Mb speeds have been tested and work.