Windows 7: IP Address Conflict: What Could It Be?

I was continuing a long, long effort to resolve a home networking problem in Windows 7.  The problem was that, if I connected more than one computer to my Netgear FS605 network switch or my Linksys WRT54GL router, I would get an error message:  "Windows has detected an IP address conflict."  I had really tried a huge number of things -- many confusedly, redundantly, or otherwise chaotically, but nonetheless striving in some ill-formed sense to solve this problem.  The solutions I had tried had worked for others; they just weren't working for me.

At this pint, it occurred to me to take my laptop, router, and switch down the way, and try them on someone else's Internet connection.  But now it was late, so that would have to wait until the next day.  But I did not think that the hardware was the problem.  A router and a switch going bad at the same time, after both had served well?

I noticed, when I tried using Google Chrome to do a search during one of those IP conflict periods (i.e., when I had two computers connected to the switch), that Chrome gave me additional information.  Besides saying "This webpage is not available" and suggesting that I reload, their "More information on this error" link gave me an error message:

Error 105 (net::ERR_NAME_NOT_RESOLVED): The server could not be found.

I did a search on that.  It produced a variety of general and Chrome-specific possible solutions.  One ChromeBoard thread went through many of the issues I had examined here and in the previous post, including changing DNS server to OpenDNS or Google (8.8.8.8 and 8.8.4.4).  It seemed the change was supposed to be made in the router, though, not on the computer, and that was different from what I had tried before.  On the theory that my problem was one that a router could sort out, but a switch could not, I went back into my router (a Linksys WRT54GL), as described in that post.  I saw that the router was set to a PPPoE connection type, which was right for my modem but may have been wrong for the router.  I changed that to DHCP.  I saved and saw that this did not solve the problem.  My next step was to try the DNS advice, but it was not clear where in the router's page I should change those numbers.  The page had both "Router IP" and "Network Address Server Settings (DHCP)" sections with DNS options.  The latter seemed right.  But there were three "static DNS" spaces to fill.  I tried the Google numbers (above) for the first two of the three.  That wasn't the solution.  Pooofont recommended unplugging the computer from the wall power socket for a half-hour.  I tried for 15 minutes.  One thing that became clear, as I perused that long thread, was that there were many problems within this Error 105.  Continuing:  I checked Win7's Start > services.msc > DHCP Client and DNS Client; mine were already started and automatic.  Another new possibility:  flush DNS using "ipconfig /flushdns."  I tried it on two computers, and then connected them to the switch; no joy.

Another possibility occurred to me.  Perhaps I had a virus.  But a virus that would immediately affect WinXP, Vista, and multiple Win7 installations, without showing any other effects, and that was not picked up by Avast, AVG, or Windows Security Essentials, all of which had been running on one of these machines or another during this process?

Around this time, I noticed that something had changed.  I had noticed it before, but now it caught my full attention.  Computer B was no longer experiencing IP conflicts when I plugged the other computers into the switch.  They continued to report such conflicts, but now computer B was OK.  Not only was it not reporting IP address conflicts, but it was now able to go online, even through the switch, when all three other computers (one running Win7, one running Vista, one running Windows XP) were also plugged into the switch and were reporting IP address conflicts.

Somehow, computer B had reached a point of functionality.  What had I (or the computer) done to achieve this?  The solution was presumably not a matter of the router or the switch; it was seemingly something about computer B in particular.  But what?  I tried to trace back through the previous post, to see what I might have been doing when this change occurred.  I had noticed it while talking to the AT&T guy, so it was before that.  But then I had to call it a day.  The system went into hibernation overnight, and when I came back to it the next morning, computer B, too, was reporting an IP conflict and was unable to go online.  Maybe it had something to do with resetting the modem, though I didn't see how.  My thinking now was that the modem could not tell what lay on the other side of the switch.  As far as the modem was concerned, it was handing out just one Internet connection.  It was up to the switch or router to arbitrate among multiple computers.

Following advice, I opened a command window in each computer (Start > Run > cmd -- or, in Win7, Start > type "cmd") and typed "ipconfig" by itself.  This produced several different results.  In computer A (running Win7) and in the Vista laptop, it did not even try to report an IPv4 address.  In computer B, it reported an IPv4 address of 192.168.131.1.  In the Windows XP machine, it reported 192.168.1.64 as the only IP address.  This seemed to suggest computer B and the WinXP machine should not be in conflict.  I unplugged the two others from the switch.  But computer B and the WinXP machine were still unable to go online.  Only when I removed three of the four machines from the switch was the one remaining machine able to connect with the Internet.  This suggested that the IPv4 address was not the issue, or at least not the only issue.

Another possibility recommended in that same thread was to go into Device Manager (a Control Panel item in Vista and Win7; under Control Panel > System > Hardware in WinXP), look under Network Adapter, and uninstall the ethernet and wireless adapters, then scan for changes and let it reinstall them.  I wasn't using wireless, so I assumed that part would be irrelevant to my situation.  The wired part was a Realtek device on both computer B and the WinXP machine.  I made sure both computers were connected to the switch, and then uninstalled the Realtek adapter.  I did not opt to delete the driver software.  Then, in the Action menu item at the top of Control Panel, I ran "Scan for hardware changes" in both computers, one at a time.  The WinXP machine started its Found New Hardware Wizard.  I couldn't get the CD drive to read the motherboard manufacturer's installation CD at that point, so I rebooted the WinXP machine and it reinstalled its wired adapter automatically during reboot, and reported an IP address conflict when it came back up.  But now computer B was not reporting a conflict.  I tried the same approach with computer A. 
It still reported a conflict and was still unable to go online.

One thing that was different about computer B, in the networking department, was that I had installed VMware Workstation there.  This seemed potentially relevant because there were VMware Virtual Ethernet Adapter for VMnet1 and VMnet 8 listed in Device Manager on computer B.  But I had had the IP address conflict problem after installing VMware, so I didn't see how that could make a difference.

At this point, I came across a suggestion to use Win7's Event Viewer.  That discussion continues in a separate post.

Using Ubuntu Linux Tools on a Windows Machine

I was using Windows XP SP3 on one machine and Ubuntu 10.04 (Lucid Lynx) on another.  There were times when I found that Ubuntu (my preferred version of the Linux operating system) could do things that Windows could not.  For example, Ubuntu was much faster and cleaner at moving large numbers of files from one folder to another.  It could also delete files and folders that Windows said could not be deleted.  So I wondered if there was a way to use Ubuntu tools on a Windows installation.  This post discusses that question.

One solution that I already knew about was to set up a dual-boot machine, with Windows XP and Ubuntu coexisting side-by-side.  If you wanted to do something in Ubuntu, you could just shut down Windows and reboot into Ubunt.  This wasn't always the world's most convenient approach.

Another solution that I was currently using was to use both of them together via virtualization.  The virtualization tool I had been using was VMware Workstation.  The way it worked for me was that I installed Ubuntu as my base layer, installed VMware Workstation in Ubuntu, and then installed Windows XP in a virtual (i.e., make-believe) "computer" inside Workstation.  So if I was working in Windows and had something I wanted to do in Ubuntu, I could just go out of the Windows virtual machine for a moment, do my thing in Ubuntu, and then resume work in Windows.  I have written lots of posts on this combination.

A different approach, for those who didn't mind rebooting and didn't want to install Ubuntu or VMware on their Windows machines, was to use an Ubuntu Live CD.  In this approach, you wouldn't reboot into an Ubuntu installation that was already present on your hard drive; you would reboot into an Ubuntu installation that was self-contained on a CD.  The CD image was free, and could easily be downloaded and burned to a CD.  It would be necessary to adjust the BIOS settings (typically, by hitting Del or perhaps F2 while the computer was booting) so as to set the CD (or DVD) drive to be the first in the boot sequence, so that the computer would try to boot from a CD (if you had inserted one into the computer) before moving on to the option of booting from your Windows installation on the hard drive.  Assuming your computer supported it (and most did, by this point), it was also possible to boot Ubuntu from a USB drive instead of a CD.

Those approaches were all familiar to me.  Two other approaches or variations were not.  The first was to use an Ubuntu live CD or USB stick, but to customize it to include Ubuntu programs that were not included on the standard Live CD.  Among the various ways of doing this, two that seemed to draw frequent attention were Reconstructor and Remastersys.  A recent post made it sound like Reconstructor was especially easy to use.  Among other possibilities, these tools would apparently allow the user to create a bootable CD or USB stick that would contain the user's own customized Ubuntu installation.

There seemed to be an endless number of variations and possibilities, some of which would require a lot of work and/or would not work well.  The last one mentioned here involved running Ubuntu, or something like it, on a Windows installation.  In essence, Ubuntu in this approach would function like just another Windows application.  As such, it would tend to be limited by the things that Windows could do.  Portable Ubuntu Tres was a recent example of this approach.

These possible approaches suggested two steps I could take, as described in more detail in separate posts.  One was to update my knowledge of virtualization alternatives to VMware Workstation.  It had been a year since I had last reviewed that topic, and I did not know whether there had perhaps been developments that would give me a superior alternative to VMware.  The other was to try my hand at burning a custom live Ubuntu DVD via Reconstructor or Remastersys.