5.13. Setting and Controlling IP sets using iptables

The essential differences between firewalld and the iptables (and ip6tables) services are:

Both use iptables tool to talk to the kernel packet filter.

To use the iptables and ip6tables services instead of firewalld, first disable firewalld by running the following command as root:

~]# systemctl disable firewalld
~]# systemctl stop firewalld

Then install the iptables-services package by entering the following command as root:

~]# yum install iptables-services

The iptables-services package contains the iptables service and the ip6tables service.

Then, to start the iptables and ip6tables services, enter the following commands as root:

~]# systemctl start iptables
~]# systemctl start ip6tables

To enable the services to start on every system start, enter the following commands:

~]# systemctl enable iptables
~]# systemctl enable ip6tables

The ipset utility is used to administer IP sets in the Linux kernel. An IP set is a framework for storing IP addresses, port numbers, IP and MAC address pairs, or IP address and port number pairs. The sets are indexed in such a way that very fast matching can be made against a set even when the sets are very large. IP sets enable simpler and more manageable configurations as well as providing performance advantages when using iptables. The iptables matches and targets referring to sets create references which protect the given sets in the kernel. A set cannot be destroyed while there is a single reference pointing to it.

The use of ipset enables iptables commands, such as those below, to be replaced by a set:

~]# iptables -A INPUT -s 10.0.0.0/8 -j DROP
~]# iptables -A INPUT -s 172.16.0.0/12 -j DROP
~]# iptables -A INPUT -s 192.168.0.0/16 -j DROP

The set is created as follows:

~]# ipset create my-block-set hash:net
~]# ipset add my-block-set 10.0.0.0/8
~]# ipset add my-block-set 172.16.0.0/12
~]# ipset add my-block-set 192.168.0.0/16

The set is then referenced in an iptables command as follows:

~]# iptables -A INPUT -m set --set my-block-set src -j DROP

If the set is used more than once a saving in configuration time is made. If the set contains many entries a saving in processing time is made.