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Android External Captive Portal Alert


We have a external captive portal configured in a Fortigate FortiOS 6 and when all works fine, but in Android devices there is a alert message as you could see in the attached screenshot.

Have you some ideia about how to solve this?

Our external captive portal has a valid HTTPS certificate, but the error occurs both if it is specified with https:// or http:// in the SSID configuration.

Do we have to install a certificate in our Fortigate? How can it be done? Our Fortigate is accessed only by IP and not a domain name. To create a SSL certificate we must have a domain associated to our Fortigate but i have no idea how that would work and how to do that.

Thanks for all help!

New Contributor II



The alert message on Android devices when connecting to an external captive portal could be due to the device detecting a potential security issue, often related to SSL/TLS certificates. Here's how you can address this:

  1. Ensure the Certificate is Trusted: Even though your captive portal has a valid HTTPS certificate, Android devices may show an alert if the certificate is not from a trusted authority or if there is a mismatch in the certificate details. Double-check that the certificate is issued by a well-known Certificate Authority (CA) and that all the details match, including the domain name.

  2. Use a Domain Name for Fortigate: To eliminate the warning, using a domain name for your Fortigate device rather than an IP address is advisable. This allows for the SSL certificate to be fully validated. 

  3. Install the Certificate on Fortigate: You need to install it on your Fortigate device.

  4. Enable HTTPS Redirection: Enabling HTTPS redirection on your Fortigate device can help avoid web browser warnings by ensuring that all connections are securely redirected to HTTPS. 

This documentation How to enable HTTPS Redirection to avoid web browser warning - Fortigate, is a guide on configuring HTTPS redirection. It likely includes steps to properly set up your SSL certificate and ensure that your captive portal is accessed securely.


Best regards, 



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