[MovedGoalPosts]

Every time you change the settings, you risk breaking the stored settings in anything else. Change it once and accept it, or don't change it at all.

MAC filtering allows the wireless router to specifically only allow a device with a matching MAC address to connect. A MAC address is effectively a serial number of any network card that it sends to other network devices. For example in Windows I can see the MAC address of my conection by going to network connections, checking the status and details for my network card where the MAC would be listed by physical properties. If you use MAC filtering, unless the router has the MAC address listed in it's permitted clients tables, then even if you have the right security password, an attempt by the appliance to connect wirelessly would fail. MAC filtering should be an option in the router's wireless security confurations admin screen.