I have a system with 3 Domain Controllers (Server 2019). One of them got out of sync (my best description) and wasn't replicating - while the other 2 seem to be working fine.
The problem seemed to be RPC errors but all 3 DCs were running together in a test lab before being deployed.
This one was deployed a month or so after the first two, having been powered down during the interim.
The failure would cause me to suspect the real network they are now in somehow - but "how?" is elusive.
I have wireshark captures taken during replication attempts but I don't see much that jumps out.
Eventually, I was advised to take the "bad" DC off the domain and re-promote it.
I've proceeded with thatprocess and have tried a lot of suggested things but so far no luck in promoting this DC.
Fortunately, this DC wasn't in the mainstream of operations and, without replication, had less configuration data on it than the others.
So, taking a step back is of little concern.
I think I did a pretty good job of bringing the DC down but I'm unsure of its status. There's a first time for everything...
I still see remnants of its name on the others for example.
So, I think the first step is to confirm that stuff is removed as required in preparation for promotion.
I've run a bunch of tools but don't know when to be happy or sad re: the results. Just no experience.
So, I'm wasting calendar time by running down blind alleys.
I *did* try to promote this DC but the process won't complete.
The process ends with what appears to be a need for further DNS configuration.
I could use some real help.