Firewalld

• Firewalld list all open ports
• Firewalld list rules
• firewall-cmd
• Allow PPTP VPN connection on firewalld

firewall-cmd is used to manage firewall (iptables). It is used by default on latest version of CentOS, RHEL.

Check firewall status

To see if firewall is running of not use

firewall-cmd --state

or

systemctl status firewalld

To disable firewalls

systemctl stop firewalld
systemctl disable firewalld

Open a port in firewall

To allow HTTP and HTTPS traffic, run

firewall-cmd --permanent --zone=public --add-service=http
firewall-cmd --permanent --zone=public --add-service=https
firewall-cmd --permanent --zone=public --add-service=ssh
firewall-cmd --permanent --zone=public --add-port=25/tcp
firewall-cmd --reload

Permanent option make the changes permanant. You need to reload firewall after using –permanent. If you want to open a port in current session and make it permanant, run the command with and with out –permanent.

Open a port range in firewall

firewall-cmd --zone=public --add-port=22-65535/tcp

Close a port in firewall

To close a port, you can use command same as you open with –add replaced with –remove.

firewall-cmd --permanent --zone=public --remove-service http
firewall-cmd --permanent --zone=public --remove-port 25/tcp

Whitelist an IP address

firewall-cmd --zone=trusted --add-source=IP_ADDR_HERE

To remove an IP, use

firewall-cmd --zone=trusted --remove-source=IP_ADDR_HERE

Firewalld Zones

Zone is a collection of rules that can be applied to a specific interface. Some useful commands are

firewall-cmd --get-active-zones
firewall-cmd --get-default-zone
firewall-cmd --list-all-zones
firewall-cmd --info-zone=public

Zones are stored in /usr/lib/firewalld/zones

Services

Services are pre-made rules for a specific application. Some useful commands are

firewall-cmd --get-services
firewall-cmd --info-service SERVICE_NAME_HERE

Services are stoed in /usr/lib/firewalld/services/ or /etc/firewalld/services/.

Save run time configuration into permanant

firewall-cmd --runtime-to-permanent

iptables

See firewall