Warning - this blog contains opinions, strong language, occasional bold text, and HTML. Viewer discretion is advised.

2010/01/16

Rebooting an SBS 2008 causes the Default Gateway to Disappear

Ran into this problem today. No matter what I did, rebooting the fully patched SBS2008 caused the server to lose Internet connectivity. Turns out, the default gateway entry on the NIC was just getting blanked out - completely gone. Running the "Connect to the Internet" or "Fix My Network" wizards did not help ("Fix my network" is fairly nebulous anyway and I don't really trust it...). Anyway, after a bunch of troubleshooting, I discovered this article:

http://www.ct-miramar.com/BlogEngine/post/SBS2008-Losing-Gateway-Settings-on-Reboot-VMWARE-ESXI-Host.aspx

Interestingly, this SBS 2008 (like nearly all of the ones I look after) is virtualized on Hyper-V, and it was showing the exact same symptom. Unfortunately, following the steps did not resolve the problem, and rebooting the server still caused the default gateway to be lost.

But, the interesting thing about the article above is that it made me realize that I probably confused the server in the first place. See, in order to facilitate a completely remote SBS swing migration, this virtualized SBS 2008 did in fact have two NICs for a period of time (something I'll get into another time). One of the entries I found at the registry key mentioned in the above article referred to "192.168.0.1", which was the gateway for my secondary NIC. So, even though that article didn't fix my problem, it helped me realize the root cause.

After focussing my search and doing a bit more looking, I found this Experts Exchange thread, which hit the nail on the head:

http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/SBS_Small_Business_Server/Q_24925134.html

Browsing to the key:

HKLM/System/CurrentControlSet/Services/Tcpip/Parameters/Interfaces/

I discovered that the "DefaultGateway" value looked like this, which is baaaad:

So, all I needed to do was remove the first line, which was blank, and causing the blank "Default Gateway" value on the NIC. Disabling and re-enabling the NIC resolved the issue, and a follow up reboot verified that the default gateway was no longer being lost.

So, watch out for this, particularly when doing SBS or Server 2008 migrations.

5 comments:

  1. 973243 The default gateway is missing on a computer that is running
    Windows Server 2008 or Windows Vista after the computer restarts if the
    default gateway is set by using the Netsh command
    http://support.microsoft.com/default.aspx?scid=kb;EN-US;973243

    The hotfix code says Vista 64 but it's also applicable to Server 2008.

    ReplyDelete
  2. I have to admit man, this is the stranges problem, but finding this page helped me out of a jam. Thanks man,,

    ReplyDelete
  3. you have posted good and very relevant information on your blog i like to visit here thanks for sharing these info with us

    sbs 2008

    ReplyDelete
  4. Just resolved a similar issue - but rather than a blank line in the multi-entry "DefaultGateway" setting, there was actually no DefaultGateway setting at all. Creating it manually seems to have fixed the issue.

    ReplyDelete
  5. I am facing the same issue right now, but I don't have a "DefaultGateway" entry in the registry. Unfortunately, manually creating the entry is not fixing my issue either.

    Is anyone having this issue?

    ReplyDelete