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[EOL/EOS] What does a ScreenOS firewall check during the Sanity Check ?



Article ID: KB7148 KB Last Updated: 20 May 2021Version: 4.0
Note: A product listed in this article has either reached hardware End of Life (EOL) OR software End of Engineering (EOE).  Refer to End of Life Products & Milestones for the EOL, EOE, and End of Support (EOS) dates.

This article provides information when packet is received and sanity check is performed.

When a debug flow basic is run, the debug output shows:  packet passed sanity check.  This KB article will list items done during a sanity check.


Here is a list of items that are done when a packet sanity check is done

  • check IP version to see if it's valid.
  • check IP length to see if it could exceed the MTU size (default=1500).
  • check IP length (plus/minus proper headers) to see if there is any mismatch between what's in the header and the real size.
  • check pak to see if it contains src-port and dst-port for creating a new session or match an existing session.
  • check dhcp pak
  • screen option check
Modification History:
2021-05-20: Minor non technical changes.
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