I was really itching to try out the new DHCP Failover goodies in Windows Server 2012. I ran into a couple weird issues when trying to configure it- hopefully I can save someone else the trouble.
When I tried to create the partner server relationship and configure failover, I'd get the following error: Configure failover failed. Error: 20010. The specified option does not exist.
We have a few custom scope options defined for our IP phones. Apparently, it won't propagate the custom option configuration during the partner relationship setup- you have to do it manually. I haven't found this step or error message documented anywhere in the context of failover configuration.
Since we only had one custom option, and I knew what it was, I just manually added it. If you don't know which options are custom and need to be copied over, it's not hard to figure out. In the DHCP snap-in on the primary server, right-click the IPv4 container and choose Set Predefined Options, then scroll through values in the Option Name dropdown with the keyboard arrows or mouse wheel until you see the Delete button light up (that'll be a custom value). Hit Edit and copy the values down, then in the same place on the partner server, hit Add and poke in the custom values. If you have lots of custom options, you can use netsh dhcp or PowerShell to get/set the custom option config.
Once the same set of custom options exist on both servers, you can do Configure Failover as normal on the scopes and it should work fine. The values of any custom options defined under the scopes will sync up just fine.
I also had one scope where Configure Failover wasn't an option. I had imported all my scopes from a 2003 DC awhile back, so I'm guessing there was something else corrupted in the scope config- just deleting and recreating the scope fixed the problem (it was on a rarely used network, so no big deal; YMMV).
Hope this helps!