ipset - 7.21-3 main

IP sets are a framework inside the Linux 2.4.x and 2.6.x kernel which can be
administered by the ipset(8) 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.
.
If you want to
.
* store multiple IP addresses or port numbers and match against the
entire collection using a single iptables rule.
* dynamically update iptables rules against IP addresses or ports without
performance penalty.
* express complex IP address and ports based rulesets with a single
iptables rule and benefit from the speed of IP sets.
.
then IP sets may be the proper tool for you.