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DHCP Failover Events and Performance

 

Applies To: Windows Server 2012 R2, Windows Server 2012

Windows Server® 2012 introduces new event logging and performance counters to support monitoring and troubleshooting of DHCP failover. See the following sections in this topic for more information:

  1. DHCP server event channels

  2. Performance counters

Note

DHCP failover-related events are also logged to the DHCP Audit Log, which by default is located at %windir%\System32\Dhcp. A DHCP-failover informational event that is commonly recorded in the DHCP Audit Log is event ID 36: 36,<date>,<time>,Packet dropped because of Client ID hash mismatch or standby server… This event is only informational and can be safely ignored. It does not indicate an error. In DHCP failover, the client messages which are broadcast are received by both the DHCP failover servers. However, only one server responds to the client messages. In case of load balance mode, the servers will hash the MAC address of a DHCP client to establish which of them must respond. In hot standby mode, only the active server responds. In both cases, the DHCP server which does not respond to the client logs this message in the audit log.

DHCP server event channels

The following DHCP Server event channels are available using Event Viewer with the path: Applications and Services Logs\Microsoft\Windows\DHCP-Server.

  1. Admin channel (Microsoft-Windows-DHCP Server Events/Admin): This channel provides DHCP server administrative event logging. For example, events are logged to this channel if a DHCP failover state of a server changes. For more information, see Administrative event logging.

  2. FilterNotifications channel (Microsoft-Windows-DHCP Server Events/FilterNotifications): This channel provides DHCP server link-layer based filtering event logging. This event channel is not used for DHCP failover related events.

  3. Operational channel (Microsoft-Windows-DHCP Server Events/Operational): This channel provides DHCP configuration auditing. For example, an event is logged if a scope on the DHCP server is added or removed from a DHCP failover relationship. For more information, see Operational event logging.

New DHCP failover-specific events have been added to these channels for administrative and operational (configuration audit) event logging.

Administrative event logging

Event Tracing for Windows (ETW) events are logged for state transition of the local server, or its partner server. These events are logged to the DHCP server Admin channel. The following data is provided as part of each state change event.

  1. The previous state of the server

  2. The current state of the server

  3. The failover relationship name

  4. The server host name or IP address

In addition to logging its own state change, the server will log changes in the state of its failover partner server. This information is communicated by state messages from the failover partner. The following table lists the values populated for the various fields in the event log.

Event Field

Value

Event ID

20252 (example ID)

Date and Time

Time of the state change

Computer

DHCP server host name or IP address

User

NETWORK SERVICE

Description

The failover state of server: <host name> for failover relationship: <relationship name> changed from: <previous state> to <current state>. The server IP address or host name corresponds to the server that has changed state. This can be the host name or IP address of the local DHCP server or the failover partner.

Note

If the previous state of the server is not known (this happens in the case of new relationship creation and when communication is interrupted), the following description will be displayed for the event: The failover state of server: <host name> for failover relationship changed to <current state>.

OpCode

FailoverStateChange

Task Category

DHCP Failover

Level

  • Error (if transitioning out of the NORMAL state or when entering into the PARTNER DOWN state)

  • Information (if transitioning into the NORMAL state)

  • Warning (for transitions between other states)

Keywords

See the following example event.

The following type of event data is logged when a server detects that it is out of time synchronization with its partner server.

Event Field

Value

Event ID

20253

Date and Time

Time of detection of time being out of sync with partner server

Computer

DHCP server host name

User

NETWORK SERVICE

Description

The server detected that it is out of time synchronization with partner server: <host name> for failover relationship: <relationship name>. The time is out of sync by: <# of seconds> seconds.

OpCode

TimeOutOfSync

Task Category

DHCP Failover

Level

Error

Keywords

An event will also be logged when a connection is established and when a connection is lost between DHCP failover partners.

Level

Opcode

Task Category

Description

Error

CommDown

DHCP Failover

Server has lost contact with failover partner server: <host name> for relationship: <relationship name>.

Information

CommUp

DHCP Failover

Server has established contact with failover partner server: <host name> for relationship: <relationship name>.

Operational event logging

The following information-level configuration audit events are logged to the DHCP server Operational channel.

Event Type

OpCode

Description

Creation of Failover Relationship

CreateFailover

A failover relationship has been created between servers: <host name> and <host name> with the following configuration parameters: Name: <value> Mode: <mode>, Maximum Client Lead Time: <value> seconds, Load Balance percentage on this server/Reserve Address percentage on standby server: <value>, Auto state switchover interval: <value> seconds Standby server: <host name>

Deletion of Failover Relationship

DeleteFailover

Failover relationship <relationship name> between <host name> and <host name> has been deleted

Addition of a scope to an existing failover relationship

AddFailoverScope

Scope <scope ID> has been added to the failover relationship <relationship name> with server <host name>

Removal of a scope from an existing failover relationship

RemoveFailoverScope

Scope <scope ID> has been removed from the failover relationship <relationship name> with server <host name>

Change MCLT

ChangeFailoverConfig

The failover configuration parameter MCLT for failover relationship <relationship name> with server <host name> has been changed from <old value> seconds to <new value> seconds

Change Auto state switchover interval

ChangeFailoverConfig

The failover configuration parameter Auto State switchover interval for failover relationship <relationship name> with server <host name> has been changed from <old value> seconds to <new value> seconds

Change Reserve Address percentage

ChangeFailoverConfig

The failover configuration parameter Reserve Address Percentage on standby server for failover relationship <relationship name> with server <host name> has been changed from <old value> to <new value>

Change Mode of failover relationship

ChangeFailoverConfig

The failover configuration parameter Mode for failover relationship <relationship name> with server <host name> has been changed from <old value> to <new value>

Change Load Balance percentage

ChangeFailoverConfig

The failover configuration parameter Load Balance percentage for failover relationship <relationship name> with server <host name> has been changed from <old value> to <new value> on this server

See the following example event.

Performance counters

Windows Server 2012 introduces the following new DHCP failover-related performance counters to the DHCP server counters:

  • Binding Updates sent per minute

  • Binding Acks received per minute

  • Binding Updates received per minute

  • Binding Acks sent per minute

  • Number of pending outbound binding updates on this server

  • Number of transitions into COMMUNICATION INTERRUPTED state

  • Number of transitions into PARTNER DOWN state

  • Number of transitions into RECOVER state

  • Number of Binding Update queue running at 90% of the maximum queue size

  • Number of Binding Updates dropped

See also

What is DHCP Failover?

DHCP Failover Relationships

DHCP Failover Modes

DHCP Failover Communications

DHCP Failover Settings

DHCP Failover Examples

Deploy DHCP Failover