SMC Networks SMC2555W-AG - Manual (Page 182)

Command Line Interface
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mac-authentication session-timeout
This command sets the interval at which associated clients will be
re-authenticated with the RADIUS server authentication
database. Use the no form to disable reauthentication.
Syntax
mac-authentication session-timeout <seconds>
seconds - Re-authentication interval. (Range: 0-65535)
Default
0 (disabled)
Command Mode
Global Configuration
Example
SMC-AP(config)#mac-authentication session-timeout 1
SMC-AP(config)#