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02.17.2004 at 10:02PM PST, ID: 20888834
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IPTables redirect internal port to outside

Asked by DingDang in Linux Networking

Tags: iptables, redirect, port

Hi,

Here is my configuration :

OS : Red Hat Linux 9.0
eth0 : 1.1.1.1 (internal IP)
eth0 gateway : -none-
eth1 : 2.2.2.2 (external Live internet IP)
eth1 gateway : 2.2.2.3

I have setup squid for all internal clients to connect to the internet using IE (the same segment on eth0). I need to setup a connection that is accepted on eth0 for port 110 and port 25 and redirect it to internet IP 3.3.3.3 port 110 and 25.

I'am using this configuration for IPtables (entered on /rc.d/rc.local) :

echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
iptables -t nat -A PREROUTING -t nat -p tcp -d 1.1.1.1 --dport 25 -j DNAT --to 3.3.3.3:25
iptables -t nat -A PREROUTING -t nat -p tcp -d 1.1.1.1 --dport 110 -j DNAT --to 3.3.3.3:110

I don't want to use MASQUERADE because clients can bypass SQUID proxy server and use 1.1.1.1 instead as a Gateway. If I don't use MASQUERADE, it wont forward the connection to outside (internet).

I need help on making people browse the internet using SQUID, and access mail directly from the internet, in the same time blocking people from using 1.1.1.1 as their gateway. All using the same IP 1.1.1.1Start Free Trial
[+][-]02.17.2004 at 10:24PM PST, ID: 10389836

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[+][-]02.17.2004 at 11:32PM PST, ID: 10390074

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[+][-]02.18.2004 at 08:35AM PST, ID: 10393966

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[+][-]02.21.2004 at 05:50AM PST, ID: 10419771

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[+][-]02.21.2004 at 09:55AM PST, ID: 10421455

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[+][-]02.22.2004 at 12:40PM PST, ID: 10427386

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About this solution

Zone: Linux Networking
Tags: iptables, redirect, port
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Solution Provided By: Redimido
Participating Experts: 2
Solution Grade: B
 
 
[+][-]02.25.2004 at 05:36PM PST, ID: 10456082

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[+][-]02.26.2004 at 01:49AM PST, ID: 10458610

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[+][-]02.26.2004 at 07:58AM PST, ID: 10461186

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[+][-]03.01.2004 at 05:08PM PST, ID: 10491485

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[+][-]03.01.2004 at 05:57PM PST, ID: 10491693

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[+][-]03.01.2004 at 11:27PM PST, ID: 10492962

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[+][-]03.04.2004 at 09:56AM PST, ID: 10516101

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