Allied Telesis AT-S25 - Manual (Page 76)

Section II: Local and Telnet Mangement
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3. From the Port Security menu, type 1 to select Port Security Mode:
Automatic.
The following prompt is displayed:
Enter new mode (A-Automatic, L-Limited, S-Secured,
K-locKed) :
4. Select the desired security level by typing the appropriate letter. For
a description of the security levels, refer to Port Security Overview
on page 68.
A change to the security level is immediately activated on a stack.
5. Type S to select Save Configuration Changes.