I am using firehol to setup my firewall with NAT.
After generating the rules I save them to /etc/iptables/iptables.rules with /etc/rc.d/iptables save
also added iptables to the daemon array:
DAEMONS=(syslog-ng hotplug dbus hal !pcmcia network hplip cups alsa netfs crond xinetd sshd samba httpd iptables kdm)
after boot iptables is started but I do not have access to the internet in the other computers of the LAN (that use the arch server as a router).
Running 'iptables restart' manually after boot everything works fine again.
Thanks in advance
The solution for your problem is quiet simple. You just have to enable "net.ipv4.ip_forward" in your /etc/sysctl.conf.
If you're using the standard /etc/rc.d/iptables script in rc.conf then check also your /etc/conf.d/iptables file. The script uses IPTABLES_FORWARD variable for setting forwarding (it probably overwrites /etc/sysctl.conf setting). The variable should be set to 1.
You were absolutely right.
sunnemer and lanrat, many thanks for your help.