All incoming connections are dropped without reply and only outgoing connections are possible. In order from least trusted to most trusted, the predefined zones within firewalld are: Regardless of how dynamic your network environment may be, it is still useful to be familiar with the general idea behind each of the predefined zones for firewalld. For a server, these zones are not as immediately important because the network environment rarely, if ever, changes. You may have strict rules in place prohibiting most traffic when operating on a public WiFi network, while allowing more relaxed restrictions when connected to your home network. Network interfaces are assigned a zone to dictate the behavior that the firewall should allow.įor computers that might move between networks frequently (like laptops), this kind of flexibility provides a good method of changing your rules depending on your environment. Zones are basically sets of rules dictating what traffic should be allowed depending on the level of trust you have in the networks your computer is connected to. The firewalld daemon manages groups of rules using entities called “zones”. Basic Concepts in Firewalldīefore we begin talking about how to actually use the firewall-cmd utility to manage your firewall configuration, we should get familiar with a few basic concepts that the tool introduces.

The behavior of some of the commands explained in this guide may vary depending on your specific configuration. Note: There is a chance that you may be working with a newer version of firewalld than was available at the time of this writing, or that your server was set up slightly differently than the example server used throughout this guide. In this guide, we will cover how to set up a firewall for your server and show you the basics of managing the firewall with the firewall-cmd administrative tool (if you’d rather use iptables with CentOS, follow this guide). Firewalld is a firewall management solution available for many Linux distributions which acts as a frontend for the iptables packet filtering system provided by the Linux kernel.

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