Make sure it is the PUBLIC IP address, and your controller is reachable through the Internet (not private address like 192.168.., 172.16.., or 10...*). You might need to configure port forwarding on your Internet router and firewall. If you are not sure, please consult with your ISP provider.
If you are using the UniFi Official Hosting: Copy the Inform URL from the dashboard after logging in and transform it by changing http to https and removing :8080/inform from the end of it.For example of the inform URL is:the controller URL will be:
Log in to your UniFi controller and click the Consoles icon (Top left).
Click the Settings icon (bottom left corner).
In the sub menu that appears next to the settings icon, click WiFi
Click Add WiFi Network to apply.
Next, in the left menu, click Insights.
Then, click Hotspot (top middle of screen).
In the right menu, click Authentication (top middle).
Under Authentication Methods -> External Portal Server -> click edit.
Next, click Settings (top right)
If you wish to support social network logins, you also need to add further IP's as per below for each network you plan to support
Facebook - 31.13.24.0/21 - 31.13.64.0/18 - 45.64.40.0/22 - 66.220.144.0/20 - 69.63.176.0/20 - 69.171.224.0/19 - 74.119.76.0/22 - 103.4.96.0/22 - 129.134.0.0/16 - 157.240.0.0/16 - 173.252.64.0/18 - 179.60.192.0/22 - 185.60.216.0/22 - 204.15.20.0/22
Twitter - 199.16.156.0/22 - 199.59.148.0/22 - 199.96.56.0/21 - 192.133.76.0/22 - 104.244.42.0/24 - 104.244.43.0/24 - 104.244.46.0/24
LinkedIn - 91.225.248.0/23 - 103.20.94.0/23 - 108.174.0.0/22 - 108.174.4.0/24 - 108.174.8.0/22 - 108.174.12.0/23 - 144.2.0.0/22 - 144.2.192.0/24 - 216.52.16.0/23 - 216.52.18.0/24 - 216.52.20.0/23 - 216.52.22.0/24 - 65.156.227.0/24 - 8.39.53.0/24 - 185.63.144.0/24 - 185.63.147.0/24 - 199.101.161.0/24 - 64.152.25.0/24 - 8.22.161.0/24
NOTE: These IP ranges are subject to change depending on the social network setup.
Click Save (bottom right)
Next, Click Branding (Top Right)
Scroll down to the Success Landing Page header
Select Custom URL.
Enter the web address of your captive portal's success page from the Ironwifi Console. (On the Captive Portal settings page in the IronWiFi console click on Success Page -> Copy the web address and enter into the Custom URL input field.