I am using Gentoo Linux with Kernel 2.4.20-r7 with iptables v.1.2.8, I tried to execute a command :

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

iptables: Invalid argument <---------- I got this.

========== quoted from 'lsmod' ==========
ipt_LOG 3384 4 (autoclean)
ipt_MASQUERADE 1336 0 (autoclean)
iptable_filter 1740 1 (autoclean)
iptable_mangle 2136 0 (autoclean) (unused)
========================================

I checked the folder '/lib/modules/2.4.20-gentoo-r7/kernel/net/ipv4/netfilter' and found these modules on my Gentoo

-rw-r--r-- 1 root root 3436 Sep 21 17:05 iptable_filter.o
-rw-r--r-- 1 root root 3780 Sep 21 17:05 iptable_mangle.o

When I checked the same path with my SuSE 8.0 and got :

-rw-r--r-- 1 root root 3256 Mar 27 2002 iptable_filter.o
-rw-r--r-- 1 root root 3660 Mar 27 2002 iptable_mangle.o
-rw-r--r-- 1 root root 22263 Mar 27 2002 iptable_nat.o

It seems a module 'iptable_nat.o' is missing on my Gentoo; and I did not compile the kernel for my SuSE box -- the kernel from the original package. I am sure the 'iptables' relative options already chosen before I compiled the kernel.

I checked the 'How-To' and help for iptables and did not get any help.

Any help ?

Thanks

I would probably recompile the kernel and make sure it has nat compiled as a module or built it