Okay, I've been struggling with this for a long time. I've looked at threads here and at Apple but nothing seems to be working. The deal: I have Comcast. That cable modem is connected by ethernet to my Airport Extreme (the single channel version.) The Airport Extreme creates a network and then the network is extended by two Airport Express units. I used to use WDS because I had an older Express that was g only, but after upgrading that one to a new n unit I switched off of WDS. If I use "Share a Public IP" everything works great, but I get Double NAT errors when uploading any file bigger than a few k. So, I switch it to Bridge Mode... and my Internet connection fails to work. Initially it appeared that the modem wasn't assigning IP addresses to the various units, so I unplugged everything and rebooted each one in sequence (first the modern, then the Extreme then Express 1 and finally Express 2) but no go. Still no Internet. Any suggestions here? I'd like to get rid of those Double NAT errors and it seems as though Bridge Mode is the way to do it, but something's either not configured right or the Comcast modem isn't assigning IPs correctly. I'm at wits end here. Sorry if this is covered elsewhere. I haven't been able to find a working solution in any of the threads.