If the 202 is *not* connected directly to the internet (if it's not the "router", or more correctly the gateway to the internet) then I wouldn't connect anything to the LAN port.
If you do you have two gateways on your system; one, the 202, from the 'lan' side of the 202 to the 'wan' side (which is actually the airport router lan) then the router to the real world. This creates unnecessary confusion and complexity.
Rather connect the Obi 'wan' port to your LAN and configure it via OBiTalk. (You won't be able to access the web page directly; you will always have to use www.obitalk.com
, if you don't like this for some reason use the expert settings and check system management/device admin/access from WAN.)
You do need the airport router to do QoS and properly favor VoIP traffic. If it doesn't you will have lousy call quality. Modern routers should do this correctly, but older ones definately do not. I don't know about Apple.
The alternative is to junk the airport router and use the OBi202 in its place. My system works fine this way (well, I junked an OpenBSD setup which did no QoS, and my provider is only 3/1Mbps, so apparently well within the 202 capabilities.)
John Bowler <firstname.lastname@example.org