Remote Desktop Connection!!!

MarkieMarkie Posts: 54Member ■■□□□□□□□□
Hey guys,

Sorry if anyone feels that my post is inappropriate in this section, as technically, its not exam related. However, it does relate to networking concepts found in the exam.

Basically, I was trying to establish a remote desktop connection, wherby the computer I was connecting to was behind a D-link router. Just to make things clear, both computers invlolved were on different subnets and were geographically separated. Both computers were running Windows XP (sp2). To make it simple, lets call the computer establishing the connection PC1 and the computer receiving/hosting the connection PC2. The router is configured to assign IP addresses dynamically.

After enabling remote desktop access on PC2 and forwarding port 3389 on the router, I was able to connect successfully (via RDP). However, I could only do this when PC2 was connected to the router via a wired connection. When PC2 was connected to the router via a wireless connection, I could not establish a connection.

It seems after further investigation, the problem related to the ip addresses the two NICs (wired and wireless) were receiving.

Originally the PC2 network had the following configuration:

D-link router (default gateway): 10.1.1.1
PC2 wired NIC : 10.1.1.2
PC3 wireless NIC: 10.1.1.3

With the above configurations, I could only establish a RDP connection through the wired NIC.

After puling out the ethernet cable a couple of times and running a few ipconfig/release + ipconfig/renew commands, the network then had the following configuartion:

D-link : 10.1.1.1
PC2 wired NIC: 10.1.1.3
PC2 wireless NIC: 10.1.1.2

And hey presto!!! I could now connect to PC2 when it was only connected to the router via the wireless NIC.

I should point out that before mucking around with testing etc, the wireless NIC had always been assigned 10.1.1.2 in the past, as the wired NIC had never been used. Somehow through testing, the wired NIC grabbed 10.1.1.2 and the wireless was assigned the next available IP address.

At all times, through testing, I only had one NIC enabled at a time.

Anyway, the question is, why would it matter what ip address the wirless NIC gets provided it is on the same subnet?

I ran a netstat -an command under both scenarios (ie. wireless NIC disconnected and wired NIC disconnected) and in both cases the computer was listening on port 3389.

Any ideas?

Im guessing it had something to do with ip address changing on the NIC, such that the router was forwarding the traffic to the wrong NIC. I wanted to remove the previously assigned addresses that were stored in the router so that I could start from scratch , i.e. 10.1.1.2 for first NIC discovered, but I could not find a way to do this.

Anyone experienced such behaviour before?
The oxen is slow but the earth is patient!!!!

Comments

  • carboncopycarboncopy Posts: 259Member
    I think I understood your question right, lol.

    If you set port forward on the router, I am assuming you are connecting from outside the network. With that being said, I believe the reason why is because when you setup Port Forwarding, you are forwarding the RDP connection to a specific IP address. Which is most likely 10.1.1.2 . Reason why it will only connect when the NIC has that IP address. Oh and BTW, you can just set a static IP on the NIC you want to RDP to so that you can try it out.
  • dynamikdynamik Posts: 12,314Banned ■■■■■■■■□□
    carboncopy wrote: »
    I think I understood your question right, lol.

    If you set port forward on the router, I am assuming you are connecting from outside the network. With that being said, I believe the reason why is because when you setup Port Forwarding, you are forwarding the RDP connection to a specific IP address. Which is most likely 10.1.1.2 . Reason why it will only connect when the NIC has that IP address. Oh and BTW, you can just set a static IP on the NIC you want to RDP to so that you can try it out.

    Exactly.
  • MarkieMarkie Posts: 54Member ■■□□□□□□□□
    Sorry for taking so long to reply. I have been ultra busy.

    Anyway, thanks a lot for clearing this up for me. It seems I had a temporary mental blank that port forwarding has to be linked to a specific ip address on the LAN.

    As you rightly say, if the ip address I configured in the router is no longer available on the LAN, the port forwarding rule will have no effect and thus the RDP connection will fail.

    Thanks again.
    The oxen is slow but the earth is patient!!!!
  • rfult001rfult001 Posts: 407Member
    Most D-Link routers should be able to Port Forward by using the hostname of the Computer as well, which would do away with that issue. So you should be establishing a connection to the routers public IP address so it can forward to the computers private IP, assuming I am understanding your scenario.
  • MarkieMarkie Posts: 54Member ■■□□□□□□□□
    Yes, you understand my scenario correctly. Although, I must admit, I have not yet seen such a feature in any of the d-link routers I have come across. It must be a feature included with the higher-end models.

    Maybe I am just lazy because when I do configure port forwarding I generally dont bother configuring static IPs anyway. The reason being, dhcp clients almost always retain their originally assigned IP address anyway (provided you dont do what I did and start pulling cables out, disabling and enabling adapters etc.)
    The oxen is slow but the earth is patient!!!!
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