Next Previous Contents 7. IP Forwarding is turned on by default in the kernel. Because of this, your network should start by denying access to everything and flushing any ipfw rules in place from the last time it was run. This script fragment should go in your network startup script. Now we have the ultimate firewall.
Nothing can get through.
This script should allow email, Web and DNS traffic through. The web server running at 192.1.2.11. We are allowing anyone on the LAN to get to outside web and DNS servers. This is not perfectly secure. The way around this is to setup a web proxy. and only allow the proxy through the firewall.