Symptoms

After upgrading to OS X Server (Mountain Lion), when selecting an AirPort base station in Server.app, this alert may appear and you may be unable to administer the base station:

"An error occurred on the server while processing a command. The error occurred while processing a command of type 'getIGDPortmaps' in plug-in 'servermgr_network'"

Resolution

Update to OS X Server v2.1 or later.

Additional Information

If similar messages persist after making portmap changes, you can use the following two Terminal commands as a workaround:

sudo /usr/libexec/PlistBuddy -c "delete :managedIGD" /Library/Server/Network/Config/autoportmap.plist
sudo /usr/libexec/PlistBuddy -c "delete :lastIGD" /Library/Server/Network/Config/autoportmap.plist