In my office, we have three servers: a Windows 2000 standalone machine, a Windows NT PDC, and an NT BDC. Before we migrated to a native Win2K mode domain, I wanted to test our backup servers by performing a restore of each server. However, as a result of budget and time constraints, our production servers were the only computers with backup devices. Our computers had been running for the past year without any major problems, so I willingly risked pulling the BDC off the network for the 2 days that I needed to perform the test restores.
Almost immediately after I pulled the BDC offline, I started to receive phone calls from remote staff who couldn't synchronize Microsoft Outlook with our Microsoft Exchange Server over the VPN, which runs on the PDC. (We're a nonprofit organization that has severe budget constraints.) From experience with the VPN, I knew that VPN connections were usually established at less than 64Kbps and occasionally failed. I determined that without the BDC to off-load host-name-resolution requests from Outlook, this service must be timing out. To solve this problem, I created a simple host file that lists the host name of our Exchange Server system and its IP address. I emailed this file to our remote users, who know to use Outlook Web Access (OWA) when they can't connect through dialing or the VPN, with the simple instructions to click the attached file and save it to the C:\windows\system folder (the clients were Windows 9x systems). Thankfully, the phone calls stopped.