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Hierarchy Level


Enable SYN cookie or SYN proxy defenses against SYN attacks. SYN flood protection mode is enabled globally on the device and is activated when the configured syn-flood attack-threshold value is exceeded.


  • syn-cookie—Uses a cryptographic hash to generate a unique Initial Sequence Number (ISN). This is enabled by default.

  • syn-proxy—Uses a proxy to handle the SYN attack.

Required Privilege Level

security—To view this in the configuration.

security-control—To add this to the configuration.

Release Information

Statement introduced in Junos OS Release 8.5; support.