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Sathapon_SS
Explorer II
February 25, 2026
Question

FortiOS 7.4.11 Issue in Transparent Mode on FortiGate 401F

  • February 25, 2026
  • 2 replies
  • 341 views

Configuration details

Mode :Transparent Mode 

Interface setting: Port x1 (internal), Port x2 (External). All traffic from the inside network passes through port x1 to port x2 to reach the internet.

 

I upgraded the FortiOS version on a FortiGate 401F from 7.4.9 to 7.4.11. After the upgrade, users were unable to access services properly. Specifically:

 

-Internal users were unable to access the Internet.

-External users were unable to access the web server located behind the FortiGate.

 

From initial traffic log analysis, I observed that packets were being sent out to the external network, but no return packets were received.

 

Due to limited maintenance time and business impact, I rolled back the FortiOS version to 7.4.9. After the rollback, all services returned to normal operation.

 

Has anyone experienced this issue with FortiOS 7.4.11?

 

Currently, I have opened a ticket with Fortinet Support, but there has been no update yet.

 

Thank you.

2 replies

Stephen_G
Moderator
Moderator
February 27, 2026

Hello Sathapon,

 

I'm glad you've opened a ticket with TAC - I'm confident they'll look into the issue shortly. In the meantime, if anyone else has any similar experiences with this issue, feel free to contribute to this thread.

Stephen_G - Fortinet Community Team
HarryTran
Staff
Staff
February 27, 2026

Did you observe if any traffic got blocked by the default policy 0?

Please share me the ticket number, I will have a closer look.