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IPTables rules - Debian Port Forward for Remote Desktop

tom_szabo
tom_szabo asked
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Last Modified: 2012-05-06
Hi,
I  need an example rule how to forward say a 3386 port to the standard 3389 port on to the local net
I have this rule, but it doesn't seam to work for some reason, is something missing?

-A PREROUTING -d 203.213.x.x -p tcp -m tcp --dport 3386 -j DNAT --to-destination 10.0.0.6:3399
-A FORWARD -i eth0 -o eth1 -d 10.0.0.6 -p tcp -m tcp --dport 3399 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT

I basically want the RDP session coming in from outside on eth0  port 3386 to be relayed onto lan ip 10.0.0.6 with port 3389
-A PREROUTING -d 203.213.x.x -p tcp -m tcp --dport 3386 -j DNAT --to-destination 10.0.0.6:3399 
-A FORWARD -i eth0 -o eth1 -d 10.0.0.6 -p tcp -m tcp --dport 3399 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT

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Commented:
Try changing the first line to:

-A PREROUTING -d 203.213.x.x -p tcp -m tcp --dport 3386 -j DNAT --to-destination 10.0.0.6 --to-ports 3389

Author

Commented:
Thanks for that but doesn't seam to be correct, I get an error message

>Unknown arg '--to-ports'

This is a guide that I gave in the past to clone the traffic of an host to a different one
http://www.bjou.de/blog/2008/05/howto-copyteeclone-network-traffic-using-iptables/

Baically, it takes advantage of TEE target (which you have to add with a patch on your existing iptables) which copies everything

On source host:
iptables -t mangle -A PREROUTING -p udp dport 9996 -j TEE gateway <IP of HOST B>

On target host:
iptables -t nat -A PREROUTING -p udp -d <IP of HOST A> dport 9996 -j DNAT to-destination <IP of HOST B>:<Port>

Commented:
Just had a double take of your original two lines.... not sure if it's a direct copy/paste from your script or not, but the dest port on both lines appears to be 3399 instead of 3389.

Author

Commented:
well, the problem is with the fact that it doesn't like the "..--to-ports 3389".."
It appears to be a syntax issue, I can't even load the "active" definitions
Commented:
It turns out --to-ports is only valid when used with -j REDIRECT.... not -j DNAT as you are using (sorry - bad recall from memory there.)

Your original syntax does look correct - maybe just double check those dest ports are set correctly on both lines?

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Author

Commented:
Well, is possibly something missing on this line?
-A FORWARD -i eth0 -o eth1 -d 10.0.0.6 -p tcp -m tcp --dport 3399 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT



Author

Commented:
Well it was correct, I had the gateway misstyped, thanks for the help
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