ERR_SSL_PROTOCOL_ERROR When trying to connect to FortiGate with any browser

[MenasheT]

Hi.

On some computers in my network, I can not log in to Fortigate and it is some computers I can not access Fortigate. After establishing an HTTPS connection - I get this error:

This site can’t provide a secure connection

192.168.41.1 sent an invalid response.

• Try running Windows Network Diagnostics.

ERR_SSL_PROTOCOL_ERROR

Is someone can help me?

Thank you!

[saneeshpv_FTNT]

Hi @MenasheT ,

This is a very generic SSL error and could be due to multiple reasons. Could you please capture the traffic between your PC and FGT using Wireshark and share the output.

Also try from different browser with recommended SSL/TLS versions (ie TLSv1.2 enabled and disabling other obsolete SSL/TLS versions) from the browser.

Best Regards

[MenasheT]

479630 47.019083 192.168.41.1 192.168.41.64 TCP 60 [TCP Retransmission] 9000 → 55452 [FIN, ACK] Seq=7247 Ack=1106 Win=180224 Len=0

[johnathan]

If you can SSH into the firewall, I would try and connect via browser while the following commands are running on your FortiGate:

di de res

di de app https -1

di de en

Might give you a rough idea of whats going on.

Looking at the crashlogs with  'di de crashlog read' is a good idea.

[mle2802]

Hi @MenasheT,

Can you please check what is the DNS server is used on that computer?

Regards,
Minh

[MenasheT]

I created a new user and the problem was solved.  Probably it was a problem with the certificates on the computer.

Thank you all!