1084
Predefined user roles
network-admin
Parameters
threshold-value: Specifies the threshold value. The value range is 1 to 1000000 in units of SYN-ACK
packets sent to an IP address per second.
Usage guidelines
The global threshold applies to global SYN-ACK flood attack detection. Adjust the threshold
according to the application scenarios. If the number of SYN-ACK packets sent to a protected server,
such as an HTTP or FTP server, is normally large, set a large threshold. A small threshold might
affect the server services. For a network that is unstable or susceptible to attacks, set a small
threshold.
With global SYN-ACK flood attack detection configured, the device is in attack detection state. When
the sending rate of SYN-ACK packets to an IP address reaches the threshold, the device enters
prevention state and takes the specified actions. When the rate is below the silence threshold
(three-fourths of the threshold), the device returns to the attack detection state.
Examples
# Set the global threshold to 100 for triggering SYN-ACK flood attack prevention in the attack
defense policy atk-policy-1.
<Sysname> system-view
[Sysname] attack-defense policy atk-policy-1
[Sysname-attack-defense-policy-atk-policy-1] syn-ack-flood threshold 100
Related commands
syn-ack-flood action
syn-ack-flood detect
syn-ack-flood detect non-specific
syn-flood action
Use syn-flood action to specify global actions against SYN flood attacks.
Use undo syn-flood action to restore the default.
Syntax
syn-flood action { client-verify | drop | logging } *
undo syn-flood action
Default
No global action is specified for SYN flood attacks.
Views
Attack defense policy view
Predefined user roles
network-admin
Parameters
client-verify: Adds the victim IP addresses to the protected IP list for TCP client verification. If TCP
client verification is enabled, the device provides proxy services for protected servers.
drop: Drops subsequent SYN packets destined for the victim IP addresses.
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