Net-filter as we all know it’s a firewall in Linux. Firewalld is a dynamic daemon to manage firewall with support for networks zones. In earlier version, RHEL & CentOS 6 we have been using iptables as a daemon for packet filtering framework. In RHEL/CentOS 7 and Fedora 21 iptables interface is being replaced by firewalld.
It’s recommended to start using Firewalld instead of iptables as this may discontinue in future. However, iptables is still supported and can be installed with YUM command. We can’t keep Firewalld and iptables both in same system which may lead to conflict.
In iptables, we used to configure as INPUT, OUTPUT & FORWARD CHAINS but here in Firewalld, the concept which uses Zones. By default, there are different zones available in firewalld, which will be discussed in this article.
The basic zone which are like public zone and private zone. To make things work around with these zones, we need to add the interface with the specified zone support and then we can add the services to firewalld.
By default, there are many services are available, one of the best feature of firewalld is, it comes with pre-defined services and we can take these services as example to add our services by simply copying them.
Firewalld works great with IPv4, IPv6 and Ethernet bridges too. We can have the separate run-time and permanent configuration in firewalld. Let’s get started how to work with zones and create our own services and much more exciting usage of firewalld.
Our Testing Environment
Operating System : CentOS Linux release 7.0.1406 (Core) IP Address : 192.168.0.55 Host-name : server1.tecmintlocal.com
Step 1: Installing Firewalld Package
1. Firewalld package is installed by default in RHEL/CentOS 7 and Fedora 21. If not, you can install it using the following YUM command.
# yum install firewalld -y
2. After firewalld package has been installed, it’s time to verify whether iptables service is running or not, if running, you need to stop and mask (not use anymore) the iptables service with below commands.
# systemctl status iptables # systemctl stop iptables # systemctl mask iptables
Stpe 2: Discussing Firewalld Components
3. Before heading up for firewalld configuration, I would like to discuss about each zones. By default there are some zones available. We need to assign the interface to the zone. A zone define that the zone was trusted or denied level to the interface to get connection. A zone can contain services & ports. Here, we’re going describe each zones available in Firewalld.
- Drop Zone: Any incoming packets are dropped, if we use this drop zone. This is same as we use to add iptables -j drop. If we use the drop rule, means there is no reply, only outgoing network connections will be available.
- Block Zone: Block zone will deny the incoming network connections are rejected with an icmp-host-prohibited. Only established connections within the server will be allowed.
- Public Zone: To accept the selected connections we can define rules in public zone. This will only allow the specific port to open in our server other connections will be dropped.
- External Zone: This zone will act as router options with masquerading is enabled other connections will be dropped and will not accept, only specified connection will be allowed.
- DMZ Zone: If we need to allow access to some of the services to public, you can define in DMZ zone. This too have the feature of only selected incoming connections are accepted.
- Work Zone: In this zone, we can define only internal networks i.e. private networks traffic are allowed.
- Home Zone: This zone is specially used in home areas, we can use this zone to trust the other computers on networks to not harm your computer as every zone. This too allow only the selected incoming connections.
- Internal Zone: This one is similar to work zone with selected allowed connections.
- Trusted Zone: If we set the trusted zone all the traffic are accepted.
Now you’ve better idea about zones, now let’s find out available zones, default zones and list all zones using the following commands.
# firewall-cmd --get-zones
# firewall-cmd --get-default-zone
# firewall-cmd --list-all-zones
Note: The output of above command won’t fit into single page as this will list every zones like block, dmz, drop, external, home, internal, public, trusted, and work. If the zones have any rich-rules, enabled services or ports will be also listed with those respective zone informations.