In computing, a firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted network and an untrusted network, such as the Internet
The first paper published on firewall technology was in 1987 when engineers from Digital Equipment Corporation (DEC) developed filter systems known as packet filter firewalls. At AT&T Bell Labs, Bill Cheswick and Steve Bellovin continued their research in packet filtering and developed a working model for their own company based on their original first-generation architecture.
HAProxy-WI offers ability to manage Firewalld automatically. It means: when you add a new frontend or listen for HAProxy with new ports or add a new server section for Nginx, HAProxy-WI will open these ports.
You can enable this function on the "Server" tabs on "Server" or "Admin area" pages. Just check checkbox in Firewalld section
For checking Firewalld rules go to the Servers -> Servers tab. Choose need server and press the "view" button in the "Firewalld" column.
On CentOS or RedHat Firewalld is installed by default. You can check it:
In output above you can see that Firewalld is run: Active: active (running). If you have another status run next:
On Ubuntu or Debian Firewalld can be installed, but before install Firewalld you have to disable pre-installed firewall - ufw: