Before starting and testing the Apache web server, the firewall will need to be modified to allow the web server to communicate with the outside world. By default, the HTTP and HTTPS protocols use ports 80 and 443 respectively so, depending on which protocols are being used, either one or both of these ports will need to be opened. If your Ubuntu system is being protected by the Uncomplicated Firewall, the following command can be used to enable only insecure web traffic (HTTP):
# ufw allow Apache
To enable only secure (HTTPS) traffic:
# ufw allow 'Apache Secure'
Alternatively, enable both secure and insecure web traffic as follows:
# ufw allow 'Apache Full'
If you are using firewalld, the following commands can be used to open the HTTP and HTTPS ports. When opening the ports, be sure to specify the firewall zone that applies to the internet facing network connection:
# firewall-cmd --permanent --zone=<zone>...