HP VPN Firewall Appliances Attack Protection Command Reference

16
Use undo defense syn-flood rate-threshold to restore the default.
Syntax
defense syn-flood rate-threshold high rate-number [ low rate-number ]
undo defense syn-flood rate-threshold
Default
The global action threshold is 1000 packets per second and the global silence threshold is 750 packets
per second.
Views
Attack protection policy view
Default command level
2: System level
Parameters
high rate-number: Sets the global action threshold for SYN flood attack protection. The rate-number
argument indicates the number of SYN packets sent to an IP address per second and is in the range of
1 to 64000. With the SYN flood attack protection enabled, the device enters attack detection state.
When the device detects that the sending rate of SYN packets destined for an IP address constantly
reaches or exceeds the specified action threshold, the device considers the IP address to be under attack,
enters attack protection state, and takes protection actions as configured.
low rate-number: Sets the global silence threshold for SYN flood attack protection. The rate-number
argument indicates the number of SYN packets sent to an IP address per second and is in the range of
1 to 64000. When the device is in attack protection state, if it detects that the sending rate of SYN
packets destined for an IP address drops below the silence threshold, it considers that the attack to the
IP address is over, returns to attack detection state, and stops the protection actions.
Usage guidelines
Adjust the thresholds according to your actual network conditions. For the protected objects that typically
have high SYN traffic, for example, HTTP server or FTP server, set a bigger action threshold to avoid
impact on normal services. For poor network conditions, or attack-sensitive networks, you can set a
smaller action threshold. If the link bandwidth of the protected network is small, you can set a smaller
silence threshold to help release the network traffic pressure.
Examples
# Configure SYN flood attack protection, set the global action threshold to 3000 packets per second and
the global silence threshold to 1000 packets per second.
<Sysname> system-view
[Sysname] attack-defense policy 1
[Sysname-attack-defense-policy-1] defense syn-flood rate-threshold high 3000 low 1000
Related commands
• defense syn-flood enable
• display attack-defense policy
defense udp-flood action drop-packet
Use defense udp-flood action drop-packet to configure the device to drop UDP flood attack packets.