Windows Server 2022 — DHCP failover communication interrupted between partners — Fix & Prevention

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution — Primary Fix
7. Solution — Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Failover relationship enters Communication Interrupted and lease balancing degrades.

Environment & Reproduction

Windows Server 2022 build 20348 DHCP pair with transient WAN/firewall packet drops.

Get-DhcpServerv4Failover
Get-DhcpServerv4FailoverStatistics
Test-NetConnection  -Port 647

Root Cause Analysis

TCP 647 blocked, clock skew, or partner state drift after unclean restart.

Quick Triage

Check peer reachability and relationship state immediately.

Get-DhcpServerv4Failover | Select Name,State,PartnerServer
Get-Service DHCPServer
w32tm /query /status

Step-by-Step Diagnosis

Inspect failover event log and lease ownership percentages.

Get-WinEvent -LogName 'Microsoft-Windows-DHCP Server Events/Operational' -MaxEvents 100
Get-DhcpServerv4ScopeStatistics
Get-DhcpServerv4FailoverStatistics

Solution — Primary Fix

Restore TCP 647 path and resynchronize relationship.

New-NetFirewallRule -DisplayName 'Allow DHCP Failover 647' -Direction Inbound -Protocol TCP -LocalPort 647 -Action Allow
Invoke-DhcpServerv4FailoverReplication -ComputerName localhost -Name 'FO-VLAN20'
Restart-Service DHCPServer

Solution — Alternative Approaches

If relationship is corrupt, recreate failover during maintenance.

Remove-DhcpServerv4Failover -Name 'FO-VLAN20' -Force
Add-DhcpServerv4Failover -Name 'FO-VLAN20' -PartnerServer  -ScopeId 10.10.20.0 -LoadBalancePercent 50 -AutoStateTransition $true -StateSwitchInterval 00:30:00

Verification & Acceptance Criteria

Relationship should return to Normal and replication timestamp should advance.

Get-DhcpServerv4Failover
Get-DhcpServerv4FailoverStatistics
Get-WinEvent -LogName 'Microsoft-Windows-DHCP Server Events/Operational' -MaxEvents 20

Rollback Plan

Revert to standalone DHCP temporarily if failover recreation fails.

Remove-DhcpServerv4Failover -Name 'FO-VLAN20' -Force
Set-DhcpServerv4Scope -ScopeId 10.10.20.0 -State Active

Prevention & Hardening

Monitor failover state and enforce time synchronization across partners.

Get-DhcpServerv4Failover | Where-Object State -ne 'Normal'
w32tm /monitor

Related Errors & Cross-Refs

Related to firewall policy baselines and packet inspection appliances dropping long-lived sessions.

Related tutorial: View the step-by-step tutorial for Windows Server 2022.

View all Windows Server 2022 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Microsoft Learn DHCP failover architecture and troubleshooting procedures.