Hi there... I'm using this script and I'd like to understand it a bit better... This is redirecting everything that comes from to port 25 to another server and this router is also a webserver.. Let me see if I understand every step 1) This rule tells netfilter to drop any packet forwarding I guess iptables -P FORWARD DROP 2) This one only accepts related and stablished packets iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT 3) This one forwards everything from the mailserver to the outside i guess iptables -A FORWARD -d 192.168.0.2 -p tcp --dport 25 -j ACCEPT 4) and this rule redirects everything in port 25 to the mailserver iptables -t nat -A PREROUTING -d 192.168.0.1 -p tcp --dport 25 -j DNAT --to-destination 192.168.0.2:25 Now these are the questions I have about netfilter 1) What does the first rules do exactly?? 2) How come if I add this rule to redirect everything from port 666 to the mailserver's ssh port it doesnt work?? iptables -t nat -A PREROUTING -d 192.168.0.1 -p tcp --dport 666 -j DNAT --to-destination 192.168.0.2:22 Is it because I have to make another rule to forward the packets comming back from the mailserver's ssh? how come is not using the one alredy in (number 2)? 3) How do I use DROP with a range of port in oder to close everyhing else to the outside? or is there other way to do it?? Thanks a lot for your help... Juan
