Bhutan ICT

Under linux OS, we use iptables to secure the machine from any other external attack. In current scenario I am forwarding the packages from local interface to external interface and i have squid configured which will be acting as transparent proxy. Only selective port numbers are open for the network. 1. Save the script to a file. 2. Give permission to execute. chmod +x filename . 3. Execute the file as follows ./filename 4. save the output of the script to system iptables file, by running the command service iptables save 5. You are done, start/restart the iptables service. service iptables restart Script: #!/bin/sh # chmod +x file name to execute # eth0 LAN # eth1 WAN # Local IP range 192.168.0.0/25 # NATing # Transparent proxy iptables -F iptables -X iptables -t nat -F iptables -t nat -X iptables -t mangle -F iptables -t mangle -X iptables -P INPUT ACCEPT iptables -P FORWARD ACCEPT iptables -P OUTPUT ACCEPT iptables -A INPUT -i lo -j ACCEPT iptables -A...

There are times when you come across an error message when you use FTP Client, the error message with be something like Failed to list directory or something like that. During such error make sure your Linux server has port 20 and 21 opened in IPTABLES. If those ports are allowed in your IPTABLES than make sure "ip_conntrack_ftp" module is loaded. Check in /etc/sysconfig/iptables-config if the following line exist: IPTABLES_MODULES="ip_conntrack_ftp" If it doesn't contain then add it or load it in module of kernal. Loading module for Kernal using rc.local file. # File: /etc/rc.local # Module to track the state of connections modprobe ip_conntrack # Load the iptables active FTP module, requires ip_conntrack modprobe ip_conntrack_ftp # Load iptables NAT module when required modprobe iptable_nat # Module required for active an FTP server using NAT modprobe ip_nat_ftp