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I'm testing FTP active and passive modes with Wireshark. The thing is that, even after I disabled Port Triggering in the firewall, so that no unsolicited connections are allowed, it's still forwarding port 20, so the ftp connections are still happening in active mode (the server initiates the data connection on port 20 and the PC accepts).

I tried restarting the router to no avail. Am I wrong that FTP should be working in passive mode if port forwarding 20-21 is disabled?

Any help much appreciated

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First of all, blocking incoming ports does not mean that an FTP client will automatically start working in the passive mode. It only means that the active mode stops working.

Second, some firewalls automatically allow FTP incoming active data ports, when the FTP client offers them to the server. For example in Windows firewall, the feature is called "StatefulFTP". Though that only works with unencrypted FTP, in which the firewall can monitor the FTP commands.

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  • Thanks for your answer. Nov 29, 2022 at 20:25

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