How to use Airport Extreme with ethernet leased line

Temporarily, if you connect your computer directly to the Ethernet line, can you get a good Internet connection that way?

If yes, then the AIrPort Extreme might work as a router for you, but you will also likely have to deal with a Double NAT error on the network. How well.....or, even if....that might work cannot be known until you try it out.

If the computer cannot connect, then what is required from your provider for the computer to connect and obtain an Internet connection?

Ah, thanks for the additional information.

Try using the DHCP Only setting on the AirPort router. Set up the router to connect using a Static IP address for the main Internet connection with the first IP address and then set up the DCHP range to use the remaining 5 static IP addresses.

I don't have this type of connection here to test, so I cannot say how well....or if.....this might work. But, in theory, this is the correct setting to use on the AirPort router.

Most people are forced to use NAT because the block of public IP is inefficient and you don't necessarily want all your devices using public access IP anyway.

The typical method of setup is using static IP on Internet tab (the bottom address). The top address is reserved as broadcast. That leaves only 4 IP you can use.. which you setup with the DHCP only setting on the network tab. Exactly as Bob has outlined. A more enterprise level router could then NAT one of those IP's but in your case you would use a second router behind the first for your local connections.. and the public addresses are used for servers etc that require public access. If you haven't done this kind of setup before.. I recommend you get a network guru in to help you.

You absolutely cannot access the route table nor can you edit it or do anything else.. this is apple we are talking about.

can I not setup a static IP on the WAN port and an usual Class C IP range for my internal DHCP pool ?

Yes, but then why have a block of public IP addresses.

The Internet tab of the Airport can be set with static IP and setup DHCP and NAT then on the Network tab.. that is fine.

You will need to use a router mode of DHCP and NAT on the AirPort router for this type of setup, as I originally suggested with a note that this may create a Double NAT error depending on how your provider has set things up.

Go ahead and use the DHCP and NAT setup, and if you see a Double NAT message, you can test to see how the network behaves with the Double NAT. If you don't see a Double NAT and the network allows you to do what you want, then all is well.