How does CentOS 8 implement that firewall service in the system? How do they benefit from using the firewall service? These are some of the things that we will tackle below.
What Is Firewall Service in CentOS 8?
In CentOS 8, a firewall service is an application or a set of applications that are used to control how network traffic is flowing inside the system. It can be used to block unauthorized access to your system.
And also to filter incoming and outgoing traffic. The firewall service can be used to stop unwanted applications from accessing the Internet.
The firewall service can also be used to allow only specific applications to access the Internet. For example, in the case of CentOS 8, you can use the firewall service to prevent any application from accessing the Internet.
Unless you specify it explicitly by using the network-related commands. So this will help you to protect your system against possible attacks from external sources.
How Does Firewall Service Work?
When you install CentOS 8, you will have a basic firewall enabled on your system by default. It will allow all incoming traffic on all ports.
By default, it will allow outgoing traffic on all ports. So basically, there is no restriction on any incoming or outgoing traffic on a system with a basic firewall service enabled on it.
The firewall service consists of two parts. One is a kernel component called a filter table and another is an Iptables command-line tool that enables and configures the kernel component (filter table).
The kernel component (filter table) can be configured by using Iptables command-line tool. Otherwise, it will remain dormant until you use Iptables command-line tool to configure it with some rules.
The Iptables command-line tool is what most people refer to as a “firewall” in Linux and CentOS 8 is not an exception. The Iptables command-line tool may be run either by itself or with some options specified.
It is to configure the kernel component (filter table) and restrict, deny or permit traffic accordingly. Since we are talking about CentOS 8 here, then I’ll use the “Iptables” command-line tool.
It is for all examples below instead of the “Firewall” command-line tool that was used in previous versions of CentOS (3 & 4). If you are using one of those older versions of CentOS.
Then replace “Iptables” with “firewall” when using the examples below with those older versions of the CentOS server.
How Does Firewall Service Works In CentOS 8?
The Iptables command-line tool alone can be used to configure the firewall service on CentOS 8. But it is not recommended.
The Iptables command-line tool comes with numerous options that can help you to configure the firewall service on your CentOS 8. For example, you can use the “-A” option to add new rules to the kernel component (filter table).
As mentioned earlier, those rules will remain dormant until they are activated by using the “-A” option. In the case of CentOS 8, the Iptables command-line tool can be used to activate those rules immediately.
So basically, there are two ways you can use the Iptables command-line tool on your system.
- Iptables command-line tool without activated rules
- Iptables command-line tool with activated rules