You can wire it directly if your Smoothwall can assign VLAN 500 to the physical WAN port and use that VLAN as the PPPoE WAN interface. Alternatively, you can have a VLAN aware switch in between the smoothwall and huawei to perform the necessary VLAN tagging/untagging or even put the DIR-615 into VLAN bridge mode ( http://unifi.athena.my/index.php?option=co...id=49&Itemid=61 ) to do this for you.

I'm not too sure if the Huawei itself can be setup to bridge a VLAN to the physical LAN port since I don't have that particular unit.

Many Unifibiz users have this issue..

I wrote that guide for people who wanted guaranteed IPTV + Internet access. You can use dd-wrt and setup Internet access fine, however getting IPTV to work is a 50/50 thing depending on your router. Not all dd-wrt flashed routers have the same amount of functionality