Technical Note: SSL warning with invalid CN error for internal CP authentication on FortiGate

[nmichael]

Description

When a user connects to a wireless network with internal captive portal authentication, the device is redirected to url: https://x.x.x.x:1003. Since FortiGate is installed with standard certificate, the user is presented with an SSL warning error of using invalid common name because it does not match the IP address of the captive portal server (or FortiGate).

Scope

All versions.

Solution

This error can be avoided only by redirecting the wireless users to  a Url that includes the FQDN of the FortiGate; instead of the FortiGate IP address. https://<FQDN>:1003

This can be implemented with the following commands:

#config firewall auth-portal
#set portal-addr <FGT FQDN>
#end

Ensure also that there is a DNS resolution entry in the DNS server for the FQDN name with the FortiGate IP address.