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NAT and Port Forwarding

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  • NAT and Port Forwarding

    Hi All,

    I am getting confused between NAT and Port forwarding so needs some one help.

    Here is the scenario.

    All the machines are connected to a LINKSYS AG241 ADSL modem/router. Router is assigned a static public ip address from ISP say 202.63.X.X.

    I have a Win2003 Machine (Let's call it AMBSRV01) which is a domain controller and exchange 2003 is installed in it. . It's configured as a DNS server and DHCP server as well. Domain name is AMB. IP Address is

    I am installing another Win 2003 machine(Let's call it AMBSRV02). This machine is connected to Domain AMB as a member server. Under TCP/IP setting, the internet gateway and DNS server is assigned the ipaddress of AMBSRV01. IP Address is This machine can access internet as well.

    Now in this scenario, let's say I want to port forward 80, so any incoming request of port 80 should go to AMBSRV02(

    Below are the setting on the router.

    Application External Port Internal Port Protocol IP Address Enabled

    HTTP 80 80 TCP YES

    This doesn't seems to work in this scenario. I can't seem to port forward 80 to Also, I have tried port forwarding to the domain controller which is port 25 and it works fine.

    Ports can only be mapped to the domain controller but not to other machines.

    Another Scenario

    Let's say, if I have another machine which is AMBCLIENT01 not connected to domain and configured to obtain IP address automatically. I can successfully do port forwarding and everything works.

    Question is what do I need to do get this working in a Windows Domain based environment ? Especially, if I need external network to see open ports on internal machines which are not domain controller.

    I hope I am making sense.

    Last edited by abhishekbhargav; 29th December 2008, 00:23.

  • #2
    Re: NAT and Port Forwarding

    Is the firewall on AMBSRV02 running?
    Is IIS running on AMBSRV02?
    Is the user account IUSR_AMBSRV02 working correctly. Password for this user in IIS must match password in ADUC.
    Joined: 23rd December 2003
    Departed: 23rd December 2015


    • #3
      Re: NAT and Port Forwarding

      Hi there,

      I have been doing further troubleshooting. I can confirm, I have disabled all the firewalls. IIS is already installed and I have already checked the settings.

      It's not a question of port 80 or 25. If I want to do some port forwarding on DC, it will work.

      If there is a machine not connected to the domain, port forwarding works on it as well.

      Any member machine which is connected to Domain
      is not been able to get port mapping and this is my main problem.

      Please let me know if you have any ideas.



      • #4
        Re: NAT and Port Forwarding

        Why SRV02 has on TCP/IP Settings, on Default Gateway field, the IP address of SRV01? From your explanations, SRV01 acts like an DNS and exchange server, not as a router. You must supply on the Default Gateway field of SRV02 (and for all workstations as well) the IP Address of the Linksys LAN interface, which I think is


        • #5
          Re: NAT and Port Forwarding

          Thanks Guys,

          This issue is solved now. I appreciate you help. Enjoy the new year !!


          • #6
            Re: NAT and Port Forwarding

            Any chance you could tell us what your findings were? Share and share alike
            Gareth Howells

            BSc (Hons), MBCS, MCP, MCDST, ICCE

            Any advice is given in good faith and without warranty.

            Please give reputation points if somebody has helped you.

            "For by now I could have stretched out my hand and struck you and your people with a plague that would have wiped you off the Earth." (Exodus 9:15) - I could kill you with my thumb.

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