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4-2
To do... Use the command... Remarks
Set the maximum number of
infected hosts that can be
concurrently monitored
system-guard ip
detect-maxnum number
Optional
30 by default
Set the maximum number of
addresses that the system can
learn, the maximum number of
times an address can be hit
before an action is taken and
the address isolation time
(presented in the number of
multiples of MAC address
aging time)
system-guard ip
detect-threshold
ip-record-threshold
record-times-threshold
isolate-time
Optional
By default, ip-record-threshold
is 30; record-times-threshold is
1, and isolate-time is 3.
The correlations among the arguments of the system-guard ip detect-threshold command can be
clearly described with this example: If you set ip-record-threshold, record-times-threshold and
isolate-time to 30, 1 and 3 respectively, when the system detects successively three times that over 50
IP packets (destined for an address other that an IP address of the switch) from a source IP address are
received within a period of 10 seconds, the system considers that it is being attacked —the system sorts
out the source IP address and decreases the precedence of delivering packets from the source IP
address to the CPU for a period of 5 times the MAC address aging time.
Configuring System Guard Against TCN Attacks
Configuration of System Guard against TCN attacks includes these tasks:
z Enabling System Guard against TCN attacks
z Setting the threshold of TCN/TC packet receiving rate
Follow these steps to configure System Guard against TCN attacks:
To do... Use the command... Remarks
Enter system view
system-view
—
Enable System Guard against
TCN attacks
system-guard tcn enable
Required
Disabled by default
Set the threshold of TCN/TC
packet receiving rate
system-guard tcn
rate-threshold rate-threshold
Optional
1 pps by default
As the system monitoring cycle is 10 seconds, the system sends trap and log information if more than
10 TCN/TC packets are received within 10 seconds by default. If the TCN/TC packet receiving rate is
lower than the set threshold within a 10-second monitoring cycle, the system will not send trap or log
information in the next 10-second monitoring cycle.