HP 3600 v2 Series Security Configuration Manual page 232

Analysis
Changing port security mode is not allowed when an 802.1X authenticated or MAC authenticated user
is online.
Solution
Use the cut command to forcibly disconnect the user from the port before changing the port security
mode.
[Device-Ethernet1/0/1] quit
[Device] cut connection interface ethernet 1/0/1
[Device] interface ethernet 1/0/1
[Device-Ethernet1/0/1] undo port-security port-mode
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