Need DHCP but get Double NAT error

Bridge Mode is the correct setting for the AirPort Extreme on your network.

Is it really not possible to set up DHCP Reservations on the modem/router? That is a very basic function of virtually any modem/router or gateway device.

So my wireless ISP suggested ignoring the problem and see how things work

While Double NAT is never recommended, you can sometimes get away with a Double NAT on a simple, basic home network.

But......and this is a big BUT......Apple's Back to My Mac feature will not work through a Double NAT, and online gaming consoles will not tolerate a Double NAT well at all.. Same for port forwarding.

Sometimes, Double NAT will noticeably slow down Internet browsing and in some cases result in a situation where some webites can be accessed while others cannot.

The bottom line.....Double NAT is not predictable......you won't know how it affects your network until you try it out on your network.

You have several options:

1) Run the modem/router "as is" and the AirPort Extreme in the correct Bridge Mode setting, and give up some reservation features

2) Run the modem/router in modem mode only......if that is possible (check with your provider)......and then run the AirPort Extreme in router mode of DHCP and NAT

3) Buy your own simple modem compatible with your provider's service.

4) If your provider will not really provide the service that you need, find a new provider that will provide you with a simple modem......not a modem/router or gateway.

Any ideas?

I doubt that we have provided any that you have not already thought about.

Ah, thanks for the additional info. If we had known more about the details of your setup, we would not have listed some of the options that we did.

There is a little used and somewhat tricky setting on the AirPort called DHCP Only that would likely do what you want. NAT could be left on at the modem in that case.

The big "IF" here is that the modem would need to issue a Static or Reserved IP address for the AirPort and the AirPort would need to be set up to connect using that Static IP address.

I don't know how well this might work but you could try to set up the Airport to connect using a Static IP address without setting up a Reserved or Static on the modem. The AirPort will request the IP address that you specify. Whether the modem honors the request is another question, since the modem may decide on its own what IP will be assigned to the AirPort.

So, if your modem is allocating IP addresses in the 192.168.1.x range, you could try setting up the AirPort to connect using a Static IP address of 192.168.1.50 or 192.168.1.100 and then tell the AirPort to use 192.168.1.51 through 192.168.1.100......or 192.168.1.101 through 192.168.1.150.....something like that.

If you have not already tried that, and have the time, you never know.

Click the Network tab at the top of the AirPort Utility screen.

Click Network Options near the bottom of the window

Change the DHCP range to read 10.0.5.101 to 10.0.5.150......the display will read 10.0.5.101 to 150

Click Save

Then click the Internet tab and set up a Static IP to connect at 10.0.5.100

Click Update

If it works, the modem will send an IP of 10.0.5.100 to the AirPort. The AirPort will issue IP addresses to connected devices using 10.0.5.101 to 150. You could specify up to 200 if you need the AirPort to issue more than 50 IP addresses.

The modem will issue normal IP addresses to other devices connected directly to the modem at 10.0.5.2 through 10.0.5.99.