Red Hat Training

A Red Hat training course is available for Red Hat Enterprise Linux

22.14. Configure the Firewall to Allow Incoming NTP Packets

The NTP traffic consists of UDP packets on port 123 and needs to be permitted through network and host-based firewalls in order for NTP to function.

22.14.1. Configure the Firewall Using the Graphical Tool

To enable NTP to pass through the firewall, using the graphical tool system-config-firewall, issue the following command as root:
~]# system-config-firewall
The Firewall Configuration window opens. Select Other Ports from the list on the left. Click Add. The Port and Protocol window opens. Click on one of the port numbers and start typing 123. Select the port 123 entry with udp as the protocol. Click OK. The Port and Protocol window closes. Click Apply in the Firewall Configuration window to apply the changes. A dialog box will pop up to ask you to confirm the action, click Yes. Note that any existing sessions will be terminated when you click Yes.