If you deselect that checkbox, you won't be allowed to connect wirelessly to the base station, even with AirPort Admin Utility. To administer the base station in this state, use one of two methods:
- Connect to the base station's LAN port with an Ethernet cable.
- Connect to a different section of the larger network -- try connecting wirelessly to a different base station and using AirPort Admin Utility via the indirect connection, for example.