Symptoms
- Restrictive rules in iptables are written automatically on server restart
- The Plesk Firewall is installed on the Plesk server
- The server is using a RHEL-based Linux distribution
- The firewalld firewall is installed and enabled on the server
Cause
The firewalld firewall and the Plesk Firewall both function by writing rules to iptables, due to which they cannot run simultaneously without causing unexpected behavior.
Resolution
1. Log into your Plesk server via SSH as the root user
2. Execute the following command
# systemctl stop firewalld && systemctl disable firewalld
Since this command disables the firewalld firewall permanently, it will not be started automatically upon server reboot.