Gentoo-Iptables, Ipchains

From Grokdoc

What the heck is this all about? Aren't we supposed to be discussing usability, rather than solutions?

iptables provide the basic firewall and packet filtering capabilities of the linux kernel. to use iptables, the kernel must be compiled with iptables support and all the needed modules (for tracking connections, like irc or ftp; or marking certain packages). there is a so called userspace utility (a programm the user can use to configure the behaviour):

your_linux_box@your_user_name:su -
your_linux_box@your_user_name:(enter password)
your_linux_box@root:emerge iptables

important: the link /usr/src/linux must point to the current used kernel source. else compilation might fail and iptables won't be usuable. after changing the kernel (up- or downgrade) iptables need to be recompiled.

check kernel version with:
uname -a

check the symbolic link in /usr/src with:
ls -l /usr/src

You can get more information from IP Tables HOWTO