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iptables question

Posted on 2009-05-19
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Last Modified: 2012-05-07
Hello everybody!
I have a linux firewall (192.168.0.1) and I would like to forward all the incoming ssh connection from LAN directed to FIREWALL IP (1.2.3.4) to a LAN machine (192.168.0.10).

Do you think it is possible? How can I do it?
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Question by:phoenix128
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3 Comments
 
LVL 11

Expert Comment

by:climbgunks
ID: 24428674

It's been a while...

change to use the correct interface:

iptables -A PREROUTING -t nat -i eth1 -p tcp --dport 22 -j DNAT --to 192.168.0.10:22
iptables -A INPUT -p tcp -m state --state NEW --dport 22 -i eth1 -j ACCEPT
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Author Comment

by:phoenix128
ID: 24429742
It is not soe easy :)
I also need to masquerade the packet to let the internal machine believe it is coming from the firewall's IP.

The problem is that I already tried to do it with DNAT and MAQUERADE or SNAT... the packet is sent to the destination's machine but it does not come back.

Any idea?
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Accepted Solution

by:
diepes earned 500 total points
ID: 24434389
1. I assume you can ping the ip's from the fw ? (Connectivity ok)
2. What is your interface names ?  eth0-192.168.0.1   eth1-1.2.3.4
3. Subnet mask's ?

from climbgunks:
iptables -A PREROUTING -t nat -i eth1 -p tcp --dport 22 -j DNAT  --to-destination192.168.0.10:22

iptables -A POSTROUTING -t nat -o eth0 -p tcp --dport 22 -j SNAT --to-source 192.168.0.1

iptables -A FORWARD -p tcp --dport 22 -d 192.168.0.10

The last rule you can make more specific if you know where the ssh will come from.
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