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[ScreenOS] Can 'tcp-syn-check' be disabled on a per-policy basis?



Article ID: KB29390 KB Last Updated: 28 Aug 2020Version: 2.0

This article provides information on disabling the 'tcp-syn-check' security feature on a per-policy level on ScreenOS devices.


As per the design of ScreenOS firewalls, 'tcp-syn-check' cannot be disabled on a per-policy or per-interface basis.

The 'tcp-syn-check' feature can only be disabled globally by issuing the command below:

unset flow tcp-syn-check


  • Care should be taken when using this command to disable 'tcp-sync-check' and allow 'tcp non-sync packets'.
  • A baseline should be taken to determine if 'tcp non-sync packets' are part of the normal traffic flow in the customer's network environment.
Modification History:
2020-08-27: Minor, non-technical edits.
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