Step 1: First, make sure the iPhone is connected to a network controlled by the firewall. On the phone, navigate to the Certificate Portal of the firewall. This can be accessed by going to
http://<IP of Interface>:4126/certportal
Step 2: Once you access the Certificate Portal, download the certificate that is available.
Step 3: After the certificate downloads, select Install to set it up as a profile on the phone. You may be prompted to enter the phone’s password. Click Install on the following two screens as well.
Step 4: The certificate will now be trusted on the device.
Step 5: On the iPhone go to
Settings>General>About>Certificate Trust Settings then enable the certificate.
You are ready to go. Don't forget this last step as it is key to get iOS to trust the certificate.