Iptables and ip information

Abc of an IP Address: http://www.geocities.com/technofundo/tech/misc/abcofip.html

Classless Inter-Domain Routing (CIDR) Overview: http://public.pacbell.net/dedicated/cidr.html

NAT & Private IP Address Ranges: http://www.jpsdomain.org/networking/nat.html

IPTables: More About It: http://testweb.oofle.com/iptables/whatis.htm

Using IPTables : http://www.netfilter.org/documentation/HOWTO/packet-filtering-HOWTO-7.html

10 minutes to an iptables-based Linux firewall: http://www.linuxworld.com/story/32837.htm