Port Redirection with iptables

[Craig Steadman]

Hi Jason
This works for me on RedHat9...

Squid config mods for transparent proxying :

        http_port       3128
        httpd_accel_host virtual
        httpd_accel_port 80
        httpd_accel_with_proxy on
        httpd_accel_uses_host_header on


Basic IPTABLES setup:

#!/bin/bash
# enable ip forward
echo 1 > /proc/sys/net/ipv4/ip_forward
                                                                                                              
/sbin/iptables --flush
/sbin/iptables -t nat --flush
/sbin/iptables -t mangle --flush
/sbin/iptables --policy INPUT ACCEPT
/sbin/iptables --policy OUTPUT ACCEPT
/sbin/iptables --policy FORWARD ACCEPT
/sbin/iptables -t nat --policy PREROUTING ACCEPT
/sbin/iptables -t nat --policy OUTPUT ACCEPT
/sbin/iptables -t nat --policy POSTROUTING ACCEPT
/sbin/iptables -t mangle --policy PREROUTING ACCEPT
/sbin/iptables -t mangle --policy OUTPUT ACCEPT
                                                                                                              
# enable destination port redirect from 80 to 3128
/sbin/iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j \
REDIRECT --to-port 3128

Cheers
	Craig



On Tue, 2003-12-16 at 23:21, Jason Cook wrote:
> I am trying to install Linux as a firewall and caching
> server with iptables and Linux.  I 
> need to do this transparently.
> 
> I installed Red Hat Linux 9.  Ran all of the updates
> nice and smooth.  Turned on ip forwarding.  
> Configured Squid...and tested it by specifying the
> servers ip address and port 3128 from the 
> browser.  Works great.  Here the options I had changed
> in the config file.
> 
> http_port 3128
> http_access deny to_localhost
> acl our_networks src 10.0.0.0/8
> http_access allow our_networks
> httpd_accel_host virtual
> httpd_accel_port 80
> httpd_accel_with_proxy on
> httpd_accel_uses_host_header on
> 
> For iptables I used 
> iptables -t nat -A PREROUTING -i eth1 -p tcp --dport
> 80 -j REDIRECT --to-port 3128
> 
> I then try to browse the internet from a client
> through the firewall and nothing.
> 
> When I run iptables -t nat -nv -L
> 
> Chain PREROUTING (policy ACCEPT 31254 packets, 3971K
> bytes)
>  pkts bytes target     prot opt in     out     source 
>              destination
>     0     0 REDIRECT   tcp  --  eth1   *      
> 0.0.0.0/0            0.0.0.0/0          tcp dpt:80
> redir ports 3128
> 
> PREROUTING is accepting packets...but none are
> processes by the redirect rule.
> 
> 
> I've been pulling my hair out for about a week.  Can
> anyone help?  
> 
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