Configuration with NAT

What is the make and model number of your modem?

Are you using a Mac or a PC to administer the AirPort Extreme?

Is this the current "tower" shaped version of the AriPort Extreme that you are asking about?

I tried to set up Airport Extreme in "Distribute a range of IP addresses" mode but I wasn't able to connect to the Internet. Where can I find some instructions on how to set up this device using NAT configuration where we use a bunch of private IP addresses internally and all computers/devices connecting to Airport Extreme get issued private IPs.

This mode is designed to distribute a series of static public IP addresses from your ISP to devices on your local network. It would typically be used if you run a number of servers (mail, web, FTP, etc.) on that local network that you want access from the Internet.

Is there a built-in firewall in Airport Extreme? When in Bridge mode, are we completely exposed to the Internet? As I mentioned when I check my computer's IP, it appears to be a regular public IP address.

The only "firewall" that is built-in the AirPort base stations is a very limited and is based on NAT. When in bridge mode, both the DHCP and NAT services are disabled and all traffic will pass-through. You would need a firewall upstream of the base station for any type of firewall security.

As Tesserax mentions, the "Distribute a Range of IP Addresses" setting is very rarely used these days, since it normally requires that your Internet Service Provider (ISP) has provided you with a fixed bank or series of Static IP addresses for your Internet connections.

If the WAN port on the AirPort Extreme is receiving a Public IP address, then you would want to use the DHCP and NAT setting for Router Mode on the device. DHCP and NAT is also known as Share a Public IP Address, depending on the version of AirPort Utility that you are using to administer the AirPort router.

When you do this....and assuming that you have not changed the DHCP Range settings for the AirPort Extreme......the AirPort Extreme will have a LAN IP Address of 10.0.1.1, and it will pass out IP addresses to other devices on your network using a range of 10.0.1.2 to 10.0.1.200.

So, all of the network devices that are connected to the AirPort Extreme will receive Private IP addresses. In other words, NAT is acting like a simple firewall to shield your network from the Internet while allowing your Public IP to be "shared" with local devices so they can connect to the Internet.

That's why we asked what make and model of modem that you are using......so that we can recommend the correct setup for the AirPort Extreme based on the modem's capabilities.

It sounds like you are using a PC to administer the AirPort Extreme, correct? That might be a problem if you have the current "tower" version of the AirPort Extreme, since the setup is not officially supported with a PC. Some settings make "take" or "stick" while others do not.

If you can answer the questions that we asked above, we should be able to provide some help for you.