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Run Windows on Multiple Domains and IP addresses The Easy Way

Written by BobW on June 5th, 2010

If you plug your laptop into different corporate networks as I do, you might run into some common Windows network problems. I will share my solutions to these problems. Since I am an Embedded Systems consultant, I frequently take my laptop computer with me when I visit clients. I connect to my clients networks for internet access. I may also need a static IP on a different subnet to talk to the development hardware project I am working on. The first problem I face is that Windows does not have a way to set up a computer with multiple IP addresses, unless you have multiple network adapters. When I connect to the development network which is isolated from their internal network, I loose internet access. Switching back and forth between networks is not very practical. The second issue is that Windows only allows computers to be part of a single Windows Domain (different from Windows Workgroups). Each client has a different domain to connect to and switching domains is even more problematic.

Windows does let you change your IP information by going through several submenus to the network setting TCP/IP properties menu. You can set up a single static IP for your computer. You can change this every time you need a different static IP. There are some problems with this method. If you do this frequently it is time consuming and error prone. If you mistype a number, it won’t work. When you change the settings, Windows does not remember your previous settings. Many times I have been debugging hardware or software that is connected via TCP/IP. Something is not working properly and I spend time tracking the problem down only to find that I typed something wrong (or forgot) to switch network settings. This method does not let you have multiple IP addresses for a single network adapter.

The second problem is that many companies require all computers to login through a Windows Domain. If you frequently move between domains, this is a problem. Windows does not allow a computer to be part of more than one domain at a time. Switching between domains is a cumbersome task. When you switch away from a domain, Windows erases the cached network credentials that verify your identity to the domain. If you are physically on site, this is not a problem. Then next time you login your credentials will be restored. However, if you are logging in remotely via a VPN, this may not work. I have had to drive back to my client’s site to log in after switching domains.

Here is my solution to first problem of operating multiple IPs on a single network connection. I keep my Windows networks settings for my office network as the default settings. I let Windows assign my network IP dynamically. When I travel to a client, my computer will automatically get its first network address dynamically. This gives me internet access. I then use WinIpConfig to add a temporary static IP for the development hardware I am working on. This wonderful utility, among other uses, allows you to instantly add a second (or third or fourth) IP address to a single network adapter. In the IP Info tab, just right click on the adapter and select add IP address.

This does not change your current IP address, it adds another one. My computer will respond to both addresses. The IP addresses can even be on total different subnets (i.e. 192.168.1.3 and 10.12.82.83). You can easily add and delete IP addresses with one click. Best of all, since these are temporary, when I reboot my laptop and connect to my office network it works because my default settings have not changed. Whenever I reboot my computer it always maintain the same base network settings. I temporarily adjust those for various client needs with WinIpConfig.

Multiple network domains are a trickier problem but I have found a solution that works for me. Many companies require that you login through a Windows domain (as opposed to a Windows workgroup) for security reasons. They may also require users to run various scripts and utilities, such as the companies approved antivirus software. These utilities may conflict with software already on your computer.

The best solution I have found so far is to setup a virtual Windows environment for each client. I use the Windows Virtual PC software, which is free, but there are other virtualizing programs as well. I use this to create a virtual Windows XP PC with the necessary utilities and login into the client’s domain. When I am done, I close the virtual PC and my actual Windows setup is unchanged. Since each virtual XP can only login to a single domain, I use a separate Virtual PC for each domain. All of the utilities and scripts are kept in separate virtual machines. They are kept isolated from my real machine.

These solutions work for me. I hope you find these tips useful for you. If you have better solutions, please let me know.

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