iptables NAT problem
I am having a problem with my iptables firewall and cannot figure out what is wrong for the life of me. It is currently set up for NAT, and all the PC's can access the internet, however if they attempt to log into any secure website, their page times out. The same goes for ftp. You can log in and authenticate to an ftp server, however if you attempt to send a file, it will timeout trying to transfer. my scripts is...:
#!/bin/bash # eth0 is connected to the internet. # eth1 is connected to a private subnet. PRIVATE=172.24.44.0/24 # Loopback address LOOP=127.0.0.1 # Delete old iptables rules # and temporarily block all traffic. iptables -P OUTPUT DROP iptables -P INPUT DROP iptables -P FORWARD DROP iptables -F # Set default policies iptables -P OUTPUT ACCEPT iptables -P INPUT DROP iptables -P FORWARD DROP # Prevent external packets from using loopback addr iptables -A INPUT -i eth0 -s $LOOP -j DROP iptables -A FORWARD -i eth0 -s $LOOP -j DROP iptables -A INPUT -i eth0 -d $LOOP -j DROP iptables -A FORWARD -i eth0 -d $LOOP -j DROP # Anything coming from the Internet should have a real Internet address iptables -A FORWARD -i eth0 -s 192.168.0.0/16 -j DROP iptables -A FORWARD -i eth0 -s 172.16.0.0/12 -j DROP iptables -A FORWARD -i eth0 -s 10.0.0.0/8 -j DROP iptables -A INPUT -i eth0 -s 192.168.0.0/16 -j DROP iptables -A INPUT -i eth0 -s 172.16.0.0/12 -j DROP iptables -A INPUT -i eth0 -s 10.0.0.0/8 -j DROP # Block outgoing NetBios (if you have windows machines running # on the private subnet). This will not affect any NetBios # traffic that flows over the VPN tunnel, but it will stop # local windows machines from broadcasting themselves to # the internet. iptables -A FORWARD -p tcp --sport 137:139 -o eth0 -j DROP iptables -A FORWARD -p udp --sport 137:139 -o eth0 -j DROP iptables -A OUTPUT -p tcp --sport 137:139 -o eth0 -j DROP iptables -A OUTPUT -p udp --sport 137:139 -o eth0 -j DROP # Check source address validity on packets going out to internet iptables -A FORWARD -s ! $PRIVATE -i eth1 -j DROP # Allow local loopback iptables -A INPUT -s $LOOP -j ACCEPT iptables -A INPUT -d $LOOP -j ACCEPT # Allow incoming pings (can be disabled) iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT # Allow services such as www and ssh (can be disabled) iptables -A INPUT -p tcp --dport http -j ACCEPT iptables -A INPUT -p tcp --dport ssh -j ACCEPT # Allow incoming OpenVPN packets # Duplicate the line below for each # OpenVPN tunnel, changing --dport n # to match the OpenVPN UDP port. # # In OpenVPN, the port number is # controlled by the --port n option. # If you put this option in the config # file, you can remove the leading '--' # # If you taking the stateful firewall # approach (see the OpenVPN HOWTO), # then comment out the line below. iptables -A INPUT -p udp --dport 5000 -j ACCEPT # Allow packets from TUN/TAP devices. # When OpenVPN is run in a secure mode, # it will authenticate packets prior # to their arriving on a tun or tap # interface. Therefore, it is not # necessary to add any filters here, # unless you want to restrict the # type of packets which can flow over # the tunnel. iptables -A INPUT -i tun+ -j ACCEPT iptables -A FORWARD -i tun+ -j ACCEPT iptables -A INPUT -i tap+ -j ACCEPT iptables -A FORWARD -i tap+ -j ACCEPT # Allow packets from private subnets iptables -A INPUT -i eth1 -j ACCEPT iptables -A FORWARD -i eth1 -j ACCEPT # Keep state of connections from local machine and private subnets iptables -A OUTPUT -m state --state NEW -o eth0 -j ACCEPT iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A FORWARD -m state --state NEW -o eth0 -j ACCEPT iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT # Masquerade local subnet iptables -t nat -A POSTROUTING -s $PRIVATE -o eth0 -j MASQUERADE |
Once this rule set is loaded, please post the output from iptables-save & lsmod
(Mask off your external ip numbers) The order of the rules is important and there appear to be some conflicting rules in the script.. Why have you chosen an Internet group of numbers for your private Net? Is your external number static or dynamic? |
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