I’ve recently configured DHCP Failover in Load Balance mode in my Lab environment setting up two Server 2012 R2 based DHCP servers. Configuring it was rather easy (at least if your aim is get in up and running quickly and you doing “spousal mode” installation) as you just go to Configure Failover on zone level and mostly all you need to do is to select mode (Standby or NLB) and type in shared secret. And this feature is so much cooler of those split scope aka 70/30 arrangements which you had to deal with in the past 🙂 But I bump into another problem in the process – my 2nd DHCP server was not authorized before I configured failover, so it showed me this red down arrow icon which definitely hints you that something is wrong.
To know what exactly these icons supposed to tell you have to read “DHCP Console Icons Reference – Server-related icons” and “DHCP Console Icons Reference – DHCP console icons added for Windows Server 2012.” MSFT documentation on these icons is a bit disjointed as first link which covers server icons is Server 2008 documentation and second is just delta of newly added icons in 2012 (icons related to newly added features like DHCP failover and DHCP policies). Why not to consolidate it into one document valid for 2012 R2?
Anyhow I know that my second DHCP server is not authorized and clicked on Authorize option, alas no errors and server keeps showing Authorize option as available. After clicking Authorize about 3 times I decided to restart DHCP console and it partially fixed things – now Authorize was grayed out so it was more clear that my DHCP server is authorized. But pesky red down arrow still persisted and I erroneously thought that it has something to do with my attempt to configure failover before authorizing second DHCP server. In the end solution turned out to be more trivial: it was necessary to restart DHCP service on 2nd server and after this DHCP console – voila, problem fixed! So once again these old consoles a bit too sluggish and often require extra refresh/restart. It is just a question of time when MMC based things will be phased out and fully replaced by PowerShell and new GUI consoles (similar to ADAC maybe?). Another example which tends to behave similarly is NLB console which is one of the oldest which still exist intact in modern versions of Windows Server).
Anyhow I now have DHCP failover configured:
Red circle with cross indicates that my 1st server is switched off, and orange arrow directed to the left means that “Failover is configured on the DHCP server.” You will see this orange arrow icon only if failover is configured and one of the servers goes down – otherwise you will see check marks in green circle everywhere with no indication of configured failover on icons level.