Resets the base station password and disables security (Access Control and RADIUS settings) for 5 minutes so that you can join the network to make changes. Its not difficult resetting airport extreme password. If you make no changes within 5 minutes, the base station reverts to its former settings. Perform this reset if you can't administer the base station because you forgot its password. Hard Resets reset the base station to an unconfigured state, but retains the last saved configuration and any profiles, allowing you to restore your base station from previous settings. Perform this reset when the base station is unresponsive, or you're troubleshooting network issues that aren't resolved by other means.
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time capsule setup guide