I recently upgraded my DNS and DHCP server from Windows 2003 to Windows 2008. I pretty painless upgrade and I thought all of my settings and installed programs stayed in tact, but that was not the case.

First, I found that Cobian Backup would not run after the upgrade, so I had to uninstall and reinstall that. No big deal, then I noticed that as my IP leases were expiring my computers on the network were no longer receiving the default gateway address. They were getting IP addresses just fine, which gave them internal network access, but they could not reach the internet without the gateway address.

I checked the DHCP setting on the server and noticed that the 003 Router option was no longer set. Apparently that did not come over as part of the upgrade. In case this trips anyone else up, the setting can be found under Server Manager..Roles..DHCP Server..[your server]..IPv4..Server Options. Right click select Configure Options, then check 003 Router and add the IP address of your router.