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Assume the following scenario, if I have a local machine (A) the requests another machine (B) using B's internal IP without regard the ports. But A and B are not on the same network, however, B has a public IP. what I want to do is when requesting machine B from machine A using B's internal IP, then some routing happens and translates B's internal IP to its public IP. How to achieve this functionality given the OS of the two machines is Ubuntu 14.04 ?

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    possible duplicate of iptables change destination IP without DNAT
    – Dusan Bajic
    Commented May 16, 2015 at 5:55
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    I think what you want here is a simple masquerade.
    – Konrad Gajewski
    Commented May 16, 2015 at 12:45
  • @dusan.bajic thanks, I tried iptables -t nat -A OUTPUT -p tcp -d 192.168.1.15 -j DNAT --to-destination 54.3.22.1 where 54.3.22.1 is B's public IP and 192.168.1.15 is B's private IP. But it did not work.
    – Yahia
    Commented May 16, 2015 at 19:35
  • @KonradGajewski Thanks. Can you please specify how to do a simple masquerade using linux commands ?
    – Yahia
    Commented May 16, 2015 at 19:36
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    @KonradGajewski No, as I don't have control on the application that is deployed on A and requests B using its private IP.
    – Yahia
    Commented May 16, 2015 at 23:06

2 Answers 2

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Ok, after a small chat with Yahia Zakaria I managed to pinpoint the problem. The app uses more than TCP to communicate, so the proper DNAT should look:

iptables -t nat -A OUTPUT -d 192.168.1.15 -j DNAT --to-destination 54.3.22.1

And that's basically it.

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Add the IP and appropriate hostnames/aliases to /etc/hosts.

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  • Thanks. But it did not work with me. Assume B's internal IP is 192.168.1.15 and B's public IP is 54.3.22.1. I put the following entry to /etc/hosts of machine A: 54.3.22.1 192.168.1.15 but did not work !
    – Yahia
    Commented May 16, 2015 at 1:24
  • Gotcha, I misunderstood the question. That's going to be pretty difficult to accomplish with just the hosts file. If your end goal is to get to the public IP that is the static IP/hostname that I would set in /etc/hosts.
    – djm
    Commented May 16, 2015 at 1:38

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