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Hierarchy Level


Configure detection and prevention of SYN flood attacks. Such attacks occur when the connecting host continuously sends TCP SYN requests without replying to the corresponding ACK responses.


On all SRX Series devices, the TCP synchronization flood alarm threshold value does not indicate the number of packets dropped, however the value does show the packet information after the alarm threshold has been reached.

The synchronization cookie or proxy never drops packets; therefore the alarm-without-drop (not drop) action is shown in the system log.


The remaining statements are explained separately. See CLI Explorer.

Required Privilege Level

security—To view this statement in the configuration.

security-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 8.5.