Not supported AirPort Extreme and Lion Mounted

You must be using an older 802.11g version of the AirPort Extreme Base Station (AEBS). If that is the case, you will need AirPort Utility version 5.6 to administer it. Unfortunately this version cannot be installed on a Mac running OS X Mountain Lion ... at least, not in the traditional sense. However, it can be installed using a utility like Pacifist.

Here are the basic steps to install version 5.6 under Mountain Lion using CharlesSoft's Pacifist:

1. If you haven't already download the AirPort Utility disk image file directly from Apple Support Download
2. Place the resultant AirPortUtility56.dmg file onto your Mac's Desktop.
3. Run Pacifist.
4. Click on the Open Package option. Find the disk image file that you just placed on your desktop, and then, click on Open.
5. The utility is located as follows: Contents of AirPortUtility56.dmg > Contents of AirPortUtility56.pkg > Contents of AirPortUtility56Lion.pkg > Applications > Utilities > AirPort Utility 5.6.app
6. Drag AirPort Utility 5.6.app to your Mac's /Applications/Utilities folder.

You can now run the AirPort Utility from the Utilities folder.

Here's another method using Terminal

Download

Airport Utility 5.6 for Lion

Open Terminal and issue the following commands in sequence

cd ~/Downloads
pkgutil --expand ./AirPortUtility56.pkg ~/Downloads/AirPortUtility56
gunzip -c < ./AirPortUtility56/AirPortUtility56Lion.pkg/Payload | sudo tar -C / -xvf - "./Applications/Utilities/AirPort Utility 5.6.app"

credits goes to Tyr