Description:

IP sets are a framework inside the Linux 2.4.x and 2.6.x kernel,
which can be administered by the ipset utility.
Depending on the type, currently an IP set may store IP addresses,
(TCP/UDP) port numbers or IP addresses with MAC addresses in a way,
which ensures lightning speed when matching an entry against a set.

ipset may be the proper tool for you, if you want to
* store multiple IP addresses or port numbers and match against the
collection by iptables at one swoop;
* dynamically update iptables rules against IP addresses or ports
without performance penalty;
* express complex IP address and ports based rulesets with one single
iptables rule and benefit from the speed of IP sets