DHCP Failover State Desynchronization (Event ID 20291) Post Subnet Re-IP

Question

Changing IP scope configurations on a DHCP Server participating in a Load Balance failover pair causes scope state synchronization to permanently fail. The partner server rejects state synchronization requests. How do we repair state desynchronization without recreating the failover relationship?

Answer 1

Hello,

When you change IP scope configurations on a DHCP server that is part of a load‑balanced failover pair, the partner server will often reject synchronization because the scope metadata no longer matches. The failover relationship expects identical scope definitions, and any mismatch in ranges, options, or reservations causes the state replication to fail. That’s why you are seeing permanent desynchronization after the scope change.

You do not need to recreate the failover relationship to repair this. The supported way to fix it is to manually reconcile the scope definitions on both partners so they are identical, then trigger a resync. On the server where you made the changes, export the scope configuration with netsh dhcp server export C:\dhcp.txt all. On the partner, stop the DHCP service, import the same configuration with netsh dhcp server import C:\dhcp.txt all, and then restart the service. This ensures both servers have identical scope definitions. Once that is done, run Invoke-DhcpServerv4FailoverReplication -ComputerName <Partner> from PowerShell to force a state resync.

If the failover relationship still shows “Not in Sync,” check the failover configuration with Get-DhcpServerv4Failover and confirm that the scope IDs match exactly. Any discrepancy in scope ranges or options must be corrected before synchronization will succeed. Also verify that the partner communication is healthy by checking Event Viewer under Applications and Services Logs → Microsoft → Windows → DHCP‑Server. Look for Event IDs 20255 and 20256 which indicate replication success or failure.

I hope you've found something useful here. If it helps you get more insight into the issue, it's appreciated to accept the answer. Should you have more questions, feel free to leave a message. Have a nice day!

Domic Vo.