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The objective that I'm trying to achieve is to be able to connect to two computers that are behind the router using RDP. My logic is that I should be able to connect to the router externally on 2 different ports. Then internally the router should be able to forward me to 2 different IP addresses using the same port. i.e. once you hit the router it can connect to each of the different IP addresses on the same port. There should be no conflict there because they are different IP addresses.

The entry that I'm trying to add in the image is getting rejected with "Port Range is overlap" (sic). I assume that the ports labeled "Internal" are the ports to connect to on the internal IP addresses.

(As an alternative I could of course configure the port for RDP on one of the internal computers to listen on 3390 instead of the default 3389. In the past I've found this to be problematic.)

Why will the router not allow me to use the same internal port on different IP addresses?

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    I think the labels "Internal" and "External" refer to where the traffic originates. In your case, when you apply that second rule named RDP2, it takes all external traffic received on port 3390 and redirects it to port 3390 on the computer located at 192.168.0.42. When traffic originates in your internal network it takes traffic destined to port 3389 and redirects it to port 3389 on that same computer. Basically, if I'm not mistaken, trying to apply both rules means you are trying to make the router forward internal traffic destined to port 3389 to both IPs and that would not be possible.
    – Ryakna
    Commented Oct 12, 2014 at 15:04
  • @Arakel - that makes some sense. So how would you enter RDP and RDP2 to achieve my goals? i.e. connect from external on ports 3389 and 3390 and then internally connect to 2 different IP addresses on port 3389.
    – Guy
    Commented Oct 13, 2014 at 4:57
  • Test if you can enter the RDP2-rule using another IP address. Since you forwarded the FTP port to 192.168.0.42, and usually FTP uses additional ports than 21, the router may have hidden rules forwarding ports overlapping with 3389.
    – user3767013
    Commented Oct 18, 2014 at 3:23

2 Answers 2

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I just ran into this problem and emailed Netgear customer support. Their response:

"NETGEAR home routers and modem routers do not support setting up port forwarding the same port numbers for different or same IP addresses. This feature is not supported or applicable with CG3000Dv2."

Seems like a silly feature for the router to lack. If anyone comes up with a workaround, I'd really like to hear about it.

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You will need to change the port RDP is listening on for one of the computers since the router (all routers actually) can only forward a port request to a single computer.

1.Start Registry Editor.

2.Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\TerminalServer\WinStations\RDP-Tcp\PortNumber

3.On the Edit menu, click Modify, and then click Decimal.

4.Type the new port number, and then click OK.

5.Quit Registry Editor.

6.Restart the computer.

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  • So if a router has an external IP (from the ISP) of 77.77.77.77 it can receive requests/traffic on any port. Internally it must be able to route those requests to any IP address and any port. I struggle to believe that route that receives a request on 77.77.77.77:3388 is unable to route that to 192.168.0.11:3399, it's one or two lines of code.
    – Guy
    Commented Mar 28, 2015 at 14:04

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