http://www.linuxjournal.com/content/advanced-firewall-configurations-ipset?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+linuxjournalcom+%28Linux+Journal+-+The+Original+Magazine+of+the+Linux+Community%29
Required linux kernel >= 2.6.35. RHEL 6.2 is have only half way support since the ipset tool is missing.
http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html-single/6.2_Release_Notes/index.html
