NAT and blocking all but Port 22 NAT and blocking all but Port 22 is a simple iptables firewall script.
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NAT and blocking all but Port 22 Description

NAT and blocking all but Port 22 is a simple iptables firewall script. NAT and blocking all but Port 22 is a simple iptables firewall script.Sample:# Internal and External Devicesdev_world=ppp0dev_int=eth0# Firewall IPaddr_int=192.168.1.1# Internal Netnet_int=192.168.1.0/24#################################################### Load Modulesinsmod ip_tablesinsmod ip_conntrackinsmod ip_conntrack_ftpinsmod ipt_stateinsmod iptable_natinsmod ipt_MASQUERADE#################################################### Delete all Rules in Filtertableiptables -F#################################################### Define new chainsiptables -N BLOCKiptables -N EXT-INTiptables -N INT-EXTiptables -N ICMP-DENYiptables -N INT-IFiptables -N EXT-IF###################################################iptables -A BLOCK -m state --state ESTABLISHED,RELATED -j ACCEPTiptables -A BLOCK -m state --state NEW -i ! $dev_world -j ACCEPTiptables -A BLOCK -j DROPiptables -A INPUT -j BLOCKiptables -A FORWARD -j BLOCK#################################################### Point to chainsiptables -A INPUT -i lo -j ACCEPTiptables -A INPUT -i $dev_int -s $net_int -j INT-IFiptables -A INPUT -d ! $addr_int -i $dev_world -s ! $net_int -j EXT-IFiptables -A INPUT -j DROPiptables -A FORWARD -d ! $net_int -i $dev_world -s $net_int -j INT-EXTiptables -A FORWARD -d $net_int -i $dev_int -s ! $net_int -j EXT-INTiptables -A FORWARD -j DROPiptables -A OUTPUT -j ACCEPT#################################################### Chain Rulesiptables -A EXT-INT -j DROPiptables -A EXT-IF -i ! $dev_world -j DROPiptables -A EXT-IF -p tcp --dport 22 -j ACCEPTiptables -A EXT-IF -p tcp --dport 5901 -j ACCEPTiptables -A EXT-IF -p tcp --dport 1024: -j ACCEPTiptables -A EXT-IF -p udp --dport 1024: -j ACCEPTiptables -A EXT-IF -j DROPiptables -A INT-IF -j ACCEPT#################################################### NAT Rules# Standard Routingiptables -A POSTROUTING -t nat -o $dev_world -j MASQUERADE -s $net_int# Port Forwarding#iptables -A PREROUTING -t nat -p tcp -d 192.168.1.1 --dport 5901 --to 192.168.1.2:5901 -j DNAT################################################### Enable IP-Forwardingecho 1 > /proc/sys/net/ipv4/ip_forward)

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