I have a Thomson TG508v2 router/modem and a brand new AirPort Extreme connected to it.
At first, I set the AirPort Extreme to "share a public IP", which enables DHCP/NAT. Everything works great but I was having the Double NAT error.
So I set the AirPort Extreme as bridge mode, which disables DHCP/NAT and let my crappy modem handle my internal network IPs.
Will this cause any performance hit in my network? I'm worried because I'll outsource this job from AirPort Extreme (premium hardware) to the crappy modem.
Before you suggest, I tried setting my modem as a bridge and configuring PPPoE on the AirPort Extreme, however it wouldn't connect to the internet, so I just dismissed leaving the modem as bridge.