I am a new CentOS Linux user and installed it on HP server. I updated /etc/sysconfig/iptables firewall config file. How do I restart a firewall on CentOS Linux version 5/6? How can I use command line to restart iptables on a CentOS server?

You can easily start or stop or restart firewall on a CentOS / Fedora / RHEL / Red Hat Linux server using the following syntax. You need to login as root user.

CentOS Linux restart iptables command

The syntax is as follows to restart an IPv4 iptables based firewall:
# service iptables restart

The syntax is as follows to restart an IPv6 iptables based firewall:
# service ip6tables restart

CentOS Linux stop iptables command

The syntax is as follows to stop an IPv4 iptables based firewall:
# service iptables stop

The syntax is as follows to stop an IPv6 iptables based firewall:
# service ip6tables stop

CentOS Linux start iptables command

The syntax is as follows to start an IPv4 iptables based firewall:
# service iptables start

The syntax is as follows to start an IPv6 iptables based firewall:
# service ip6tables start

CentOS Linux get status of iptables command

The syntax is as follows to status of an IPv4 iptables based firewall:
# service iptables status

The syntax is as follows to status of an IPv6 iptables based firewall:
# service ip6tables status