Configuring and Monitoring Port Security
Reading Intrusion Alerts and Resetting Alert Flags
Figure 13-12. Example of Multiple Intrusion Log Entries for the Same Port
The log shows the most recent intrusion at the top of the listing. You cannot
delete Intrusion Log entries (unless you reset the switch to its factory-default
configuration). Instead, if the log is filled when the switch detects a new
intrusion, the oldest entry is dropped off the listing and the newest entry
appears at the top of the listing.
Keeping the Intrusion Log Current by Resetting Alert
Flags
When a violation occurs on a port, an alert flag is set for that port and the
violation is entered in the Intrusion Log. The switch can detect and handle
subsequent intrusions on that port, but will not log another intrusion on the
port until you reset the alert flag for either all ports or for the individual port.
On a given port, if the intrusion action is to send an SNMP trap and then disable
the port (send-disable), and an intruder is detected on the port, then the switch
sends an SNMP trap, sets the port’s alert flag, and disables the port. If you re-
enable the port without resetting the port’s alert flag, then the port operates
as follows:
■ The port comes up and will block traffic from unauthorized devices it
detects.
■ If the port detects another intruder, it will send another SNMP trap, but
will not become disabled again unless you first reset the port’s intrusion
flag.
This operation enables the port to continue passing traffic for authorized
devices while you take the time to locate and eliminate the intruder. Other-
wise, the presence of an intruder could cause the switch to repeatedly disable
the port.
Note on
Send-Disable
Operation
13-35
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