The Log shows "TCP packet received on non-existent/closed connection" message.
03/26/2020 22 16841
This Log message is displayed when the SonicWall firewall receives a TCP packet after a particular connection was closed.
This is a generic error message as there are a number of root causes that can create this error. For example: A packet was delayed in transition for some reason and reaches the SonicWall after the connection was closed. The SonicWall Firewall drops the packet and logs the message.
Note: This log message is categorized under Network Debug. In OS Enhanced it is under the Legacy Category. Possible Solutions
- Uncheck Network Debug, Denied LAN IP and VPN Stats Log Categories (On OS Enhanced: uncheck Legacy Category).
- Increase the Inactivity timeout of the rules on the SonicWall.
- VPN tunnels: You may need to increase activity timeout on the LAN to VPN as well as the VPN to LAN rule to avoid timeout conditions.
- Make sure the upstream device, source and destination computers connecting to each other do not have latency.
- Upgrade Firmware to the latest version. You may wish to contact technical support to determine whether or not a firmware upgrade is an appropriate action for your environment and issue.
You can check the most recent firmware versions available for your product through your MySonicWall account.
- Log into your MySonicWall account at http://www.mysonicwall.com/.
- In MySonicWall, click Downloads in the left navigation pane to display the Download Center screen.
- Select your product in the Software Type drop-down list to display available firmware versions.
- To download the firmware to your computer, click the link for the firmware version you want. You can download the Release Notes and other associated files in the same way.