Iptables should be installed by default on all CentOS 3.x, 4.x and 5.x installations. You can check to see if iptables is installed on your system by:

# rpm -q iptables

Sample output

iptables-1.3.5-5.3.el5_4.1

How to enable firewall

Login as root and type the following command

# /etc/init.d/iptables start
# chkconfig iptables on

If you are using IPv6, enter:

# /etc/init.d/ip6tables start
# chkconfig ip6tables on

And to see if iptables is actually running, we can check that the iptables modules are loaded, type the following command

# lsmod | grep ip_tables

Something look like:

ip_tables              29288  1 iptable_filter
x_tables               29192  6 ip6t_REJECT,ip6_tables,ipt_REJECT,xt_state,xt_tcpudp,ip_tables

How to disable firewall

Login as root and type the following command

# /etc/init.d/iptables stop
# chkconfig iptables off

If you are using IPv6, enter:

# /etc/init.d/ip6tables stop
# chkconfig ip6tables off

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