Symptoms
Consider the following scenario:
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You have two DHCP servers that are running Windows Server 2012 R2.
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You configure the servers as a failover cluster.
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You set up multiple DHCP scopes and multiple IP networks.
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You put a client computer on one of the IP networks and confirm that it receives an IP address from one of the scopes.
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You move the client computer to a different IP network.
In this scenario, an Error event that resembles one of the following Event ID 20291 events is logged under the "Applications and Services Logs/Microsoft/Windows/Microsoft-Windows-DHCP Server Events" path in Event Viewer:
Source: Microsoft-Windows-DHCP-ServerDate: date/timeEvent ID: 20291Task Category: DHCP FailoverLevel: ErrorUser: NETWORK SERVICEComputer: DHCP-NODEDescription: A BINDING-ACK message with transaction id: number was sent for IP address: address with reject reason: (Fatal conflict exists: address in use by other client) to partner server: other_dhcp_node for failover relationship: failover_name.
Source: Microsoft-Windows-DHCP-ServerDate: date/timeEvent ID: 20291Task Category: DHCP FailoverLevel: ErrorUser: NETWORK SERVICEComputer: DHCP-NODEDescription: A BINDING-ACK message with transaction id: Transaction_Number was sent for IP address: IP_Address with reject reason: (Reject Reason Unknown) to partner server: DHCP_Partner_Server for failover relationship: DHCP_Failover_Relationship_Name.
Resolution
Update information
The fix that resolves this problem is included in the November 2014 update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2.Note Before you install this update, you have to first remove the failover relationship, install the update to both DHCP nodes and restart them, and then reestablish the failover relationship.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the terminology that Microsoft uses to describe software updates.
