"This How-To is performed on a Debian Sarge 3.1 box, though the
commands and syntax should work for any linux distro. Before you
can configure iptables, you first must ensure that it has been
compiled into the kernel, and that you have the proper userland
"You should have a config file from when the kernel was
compiled. Grep'ing it for 'CONFIG_IP_NF' should produce '=y' or
'=m' for most of the lines/options. Here you see that
'CONFIG_IP_NF_IPTABLES' was compiled as a kernel module..."