652 
Syntax 
syn-ack-flood threshold threshold-value 
undo syn-ack-flood threshold 
Default 
The global threshold is 1000 for triggering SYN-ACK flood attack prevention. 
Views 
Attack defense policy view 
Predefined user roles 
network-admin 
Parameters 
threshold-value: Specifies the threshold for triggering SYN-ACK flood attack prevention. 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 SYN-ACK flood attack detection for non-specific IP addresses. 
Adjust the threshold according to the application scenarios. If the number of SYN-ACK packets 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. 
Examples 
# Set the global threshold to 100 for triggering SYN-ACK flood attack prevention in 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 action is taken against detected SYN flood attacks. 
Views 
Attack defense policy view