You experience one or more of the following issues when you use Dynamic Host Configuration Protocol (DHCP) failover in Windows Server 2012:
- Two DHCP servers in a failover relationship report different failover states. This issue occurs even though both servers are connected to the network.
- Some lease information is not replicated successfully between the two DHCP servers even though both servers report a typical failover state.
These are known issues with DHCP failover in Windows Server 2012. These issues occur when the following conditions are true:
- Existing scopes are migrated to Windows Server 2012 by using netsh dhcp server export and netsh dhcp server import commands. Or, an existing DHCP server is upgraded to Windows Server 2012.
- A scope has one or more inactive reservations when the scope is migrated or when the DHCP server is upgraded.
To resolve these issues, apply the cumulative update package that is described in the following article in the Microsoft Knowledge Base:
2756872 Windows 8 Client and Windows Server 2012 General Availability Cumulative UpdateNote To resolve the issues in an existing failover relationship, delete the relationship before you apply the update package, and then re-create the failover relationship. These issues do not occur if a failover relationship is created after you apply the cumulative update package.
To work around these issues, use the following Windows PowerShell commands to migrate scopes to Windows Server 2012:
Export-DhcpServer $env:SystemRoot\System32\Dhcp\Temp.txt -Leases
Import-DhcpServer -BackupPath $env:SystemRoot\System32\Dhcp\Backup -File $env:SystemRoot\System32\Dhcp\Temp.txt -ScopeOverwrite -Leases
These issues do not occur if scopes are migrated by using the Windows PowerShell commands Export-DhcpServer and Import-DhcpServer.