One of my domain controllers corrupted and the secondary DC has not come online since. I have found the following error message in the event log with event ID 1126.
Active Directory Domain Services was unable to establish a connection with the global catalog.
Additional Data
Error value:
1355 The specified domain either does not exist or could not be contacted.
Internal ID:
3201641
User Action:
Make sure a global catalog is available in the forest, and is reachable from this domain controller. You may use the nltest utility to diagnose this problem.
On the remaining domain controller, edit the registry value at HKLM\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters\SysvolReady
It should initially be 0. Set it to 1 and restart Active Directory Domain Services.