to NAT or not to NAT

I'm very confused. I just updated my old Airport Extreme to one of the new ones with dual band. It is connected to a Motorola 2210 modem with AT&T DSL. After I had it going for a while, Airport Utility popped up and said the Extreme had a problem, namely "double NAT". I had not a clue as to what this meant, but after searching I found information suggesting that I should put the modem in bridged mode and change the Extreme's Internet connection from Ethernet to PPPoE. I did that and everything seems to be running well, other than that AT&T periodically drops my Internet connection, but that problem has been going on for a long time.

Because I don't know what NAT is doing, I am left with the question of whether I need to have it on or not. I have tried running the Extreme with it not enabled and I haven't seen any difference. Can anyone tell me why I should or should not have it enabled? Also, when I have it enabled, it gives me "Enable default host at 10.0.1.243". Is this correct? Thanks.

Message was edited by: Fred Tedsen2

Mac OS X (10.4.11)

Posted on Mar 24, 2009 1:53 PM

Apr 4, 2009 10:41 AM in response to Tesserax

Hi Tesserax,

Wanting to learn more about the Motorola - Netopia modem and following your suggestion that the modem should be supplying the PPPoE, NAT etc, I thought I would try this approach...if for no other reason than to experiment a bit.

I had always had my modem in bridge mode with the TC set up to provide the PPPoE, NAT, etc services, which worked well. I reset the modem back to factory defaults, logged in to the configuration page and selected PPP on the modem, saved and restarted.

I tried different settings on the TC for connect using "ethernet", share a single IP address and bridge mode. I thought bridge would work best since the modem was now set up for PPPoE, etc., but never could get an internet connection no matter what I tried. Same with other settings, so I went back to my original set up.

Today, I decided to experiment some more, logged back into the modem after resetting to default and studied some of the set up options under the Advanced tab. I found an option under Connection Configuration that allowed a choice between "use a private IP address" or "use a public IP address". The default was set to "private", but remembering that the TC had an option to "share a public IP address" with the "connect using ethernet" settings, I thought I would give this a shot. That did the trick. Solid connection now. I'll try this for a few weeks to see how the connection holds up vs. having the TC provide the services.

Just thought I would pass the info about the default settings on the Motorola on to you in case you see some questions about this. Then again, as an expert, you probably already knew this!