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problem with server 2003 NAT

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  • problem with server 2003 NAT

    Before i tell you the problem let me explain you the kind of environment i have setup here.

    I have four computers running WinXP Pro as clients and one server running server 2003 Ent. Edition. All of these clients are joined in the domain of the server and are also provided IP address through the Server 2003 DHCP Server in the range - All the pc's have the subnet mask of and default gateway of and primary dns server of is the ip address of my server 2003.

    Now, i have one ADSL internet connection at home, which has to be connected using PPPoE. Now, in order for all my clients to have access to internet i setup NAT on my server 2003. My Server 2003 has got two network adapters, one connecting to the ADSL cable(directly coming from phone) and other adapter connected to the my local switch(no router) from where all other client pc's are connecting. Now, on my Server 2003 I have setup NAT with basic options like the default provided basic firewall with routing not enabled and also there are no software firewall as well running on my server or client.

    My problem now is, the internet surely is working on my clients but i assume some ports have got blocked by server. Like, on my clients some pc's are using mirc and messengers like (icq, msn). Now, my clients complaint that they are not able to make there dcc server running in mirc and that they are not able to connect to msn or icq messenger. If i directly connect the adsl cable to these same computers then everything works fine, but when the connection is through the server 2003 then these programs dont function well.

    Can anybody please tell me what i can do to enable these ports or enable/disable any other option which might be causing the problem. Thanks.

  • #2
    Re: problem with server 2003 NAT

    > Can anybody please tell me what i can do to enable these ports or enable/disable any other option which might be causing the problem

    The problem might not be the server, it could be the modem. The thing is, NAT is just a hack. Most protocols don't work directly over a NAT, but require some translation code. For instance, to replace some external IP addresses by internal, and vice versa. Especially chat and video protocols suffer from this problem. uPNP can help somewhat with this.

    Some things you might try.
    - enable uPNP on the modem and the workstations
    - if you have specific workstations for specific protocols, you can try NAT port mapping.


    • #3
      Re: problem with server 2003 NAT

      Thanks for the reply wkasdo. But can you please provide me with some more details or some online resource, on how to do NAT port mapping on server 2003. I have never done this before and i am kind of new to networking.