Hi,

Is your guest portal on the ISE ? In the ISE , there is only HTTPS port allowed to configure under Guest portal and no option of http port is there , So I dont think so. You also might be using port 8443 in the external web-auth redirection URL under security tab.

Now even if you put a valid certificate on the ISE which hosts external guest portal , still you would receive certificate warning as long as you use local web server of the controller which is its virtual ip address.This is because even if the external web server where page is hosted for example has a valid certificate , even then internal virtual ip address is presented to the client.

So

> either you trust them in your browser so that you dont receive certificate warnings

>or else have a valid certificate on the controller and external web server. 

> or use http for web authentication in the controller and also http to external hosted page, then also you can get rid of these certificates.

Regards

Dhiresh