Awhile back I setup a virtual machine to support the Sioux Falls .NET User Group ( website. This was meant to be a quick and easy solution to help get the DNUG community a place to post information.

Being a DNUG community, and trying to stay up to date, we chose to install Server 2008. While I’ve used Server 2008 at home for testing purposes, our data center is pretty much capped at Server 2003 R2 instances. Having had previous experience with Server 2008, I didn’t think there would be much of a problem.

I was wrong.

Since day 1 this server was giving me problems. Almost all of them related to a random IP Conflict issue. Naturally I’m thinking I must have messed up my inventory and used a duplicate IP. No big deal. I correct it and move on with life. Then the problem happens again, and again, and again. Eventually, I know somethings wrong, but I haven’t had much time to look into it… until now.

Apparently there is a known issue with Server 2008 and Address Resolution Protocol (ARP). When a Server 2008 server issues an ARP request to determine whether an IP address is being used, the device “might” incorrectly answer ARP request and an IP address conflict is reported.

What does this mean in the real world? Basically if you assign an IP, it works for awhile. If you reboot, the computer checks for an IP but sees it’s used (even though it’s not) and you get screwed. So say you have automatic windows updates? Your server reboots to apply the update and now you no longer have Internet access. Good luck fixing that remotely.

Anyway, there is a crappy registry hack to fix this:

  1. Locate registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
  2. Add a new DWORD value, “ArpRetryCount
  3. Set the value to 0.
  4. Reboot.

It’s not the most glorious fix in that you’re basically just throwing out a basic part of networking, but it works I guess. Yay Microsoft.

On the plus side, our Sioux Falls .NET User Group site is now online and stable. Now we’ll need to actually focus and spend some time putting together some content using the new EPiServer software that Seth was able to get a license donated to our DNUG. Way to go Seth!


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