Allied Telesis AT-S20 - Manual (Page 92)

Security/Source Address Table
6-18
Disable the Port (no SNMP trap)
Use this configuration when you want the switch to automatically
disable the port when an intruder is detected. Once the switch
software disables a port because of an intruder, no source address
can use that port. The port remains disabled until you manually
enable it.
Note
When the Security feature is used to disable a port, the MAC
addresses are not deleted until the port is re-enabled. This allows the
user to check the MAC address display to see which MAC addresses
came in on the specified port.
Transmit SNMP Trap and Disable port
Use this configuration if you want to send an SNMP trap message
and disable the port at the same time during an intrusion. Once the
switch software disables a port because of an intruder, no source
address can use that port. Note that when the port becomes
disabled by enabling the securing feature, the MAC addresses
associated with the specified port are not removed immediately
from the table. However, the addresses will be removed from the
table as the MAC addresses age out.
No Action (default) (No trap; port state unchanged)
In this default setting, an SNMP trap is not sent and the port state
remains unchanged when an intruder is detected.