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Monitoring DHCP Server Performance

Updated: October 16, 2008

Applies To: Windows Server 2008

Windows Server 2008 provides a set of DHCP server performance counters that can be used to measure and monitor various aspects of server activity, such as the following:

  • All types of DHCP messages sent and received by the DHCP service.

  • The average amount of processing time spent by the DHCP server per message packet sent and received.

  • The number of message packets dropped because of internal delays at a DHCP server computer.

To access these counters, you must use System Monitor.

By default, performance monitoring of DHCP servers is available for use after the DHCP service component is installed. DHCP performance is measured using the following metrics and counters:

 

Name Description

Packets Received/sec

The number of message packets received per second by the DHCP server. A large number indicates heavy DHCP-related message traffic to the server.

Duplicates Dropped/sec

The number of duplicated packets per second dropped by the DHCP server. This number can be affected by multiple DHCP relay agents or network interfaces forwarding the same packet to the server. A large number here indicates that either clients are probably timing out too fast or the server is not responding fast enough.

Packets Expired/sec

The number of packets per second that expire and are dropped by the DHCP server. When a DHCP-related message packet is internally queued for 30 seconds or more, it is determined to be stale and expired by the server. A large number here indicates that the server is either taking too long to process some packets while other packets are queued and becoming stale, or traffic on the network is too high for the server to manage.

Milliseconds per packet (Avg.)

The average time in milliseconds used by the DHCP server to process each packet it receives. This number can vary depending on the server hardware and its I/O subsystem. A sudden or unusual increase might indicate a problem, either with the I/O subsystem becoming slower or because of processing overhead on the server computer.

Active Queue Length

The current length of the internal message queue of the DHCP server. This number equals the number of unprocessed messages received by the server. A large number might indicate heavy server traffic.

Conflict Check Queue Length

The current length of the conflict check queue for the DHCP server. This queue holds messages without responses while the DHCP server performs address conflict detection. A large value here might indicate that Conflict Detection Attempts has been set too high or that there is unusually heavy lease traffic at the server.

Discovers/sec

The number of DHCP discover messages (DHCPDISCOVERs) received per second by the server. These messages are sent by clients when they start on the network and obtain a new address lease. A sudden or unusual increase indicates a large number of clients are attempting to initialize and obtain an IP address lease from the server, such as when a number of client computers are started at any given time.

Offers/sec

The number of DHCP offer messages (DHCPOFFERs) sent per second by the DHCP server to clients. A sudden or unusual increase in this number indicates heavy traffic on the server.

Requests/sec

The number of DHCP request messages (DHCPREQUESTs) received per second by the DHCP server from clients. A sudden or unusual increase in this number indicates a large number of clients trying to renew their leases with the DHCP server. This might indicate that scope lease durations are too short.

Informs/sec

The number of DHCP information messages (DHCPINFORMs) received per second by the DHCP server. DHCP inform messages are used when the DHCP server queries for the directory service for the enterprise root and when dynamic updates are being performed on behalf of clients by the server.

Acks/sec

The number of DHCP acknowledgment messages (DHCPACKs) sent per second by the DHCP server to clients. A sudden or unusual increase in this number indicates that a large number of clients are being renewed by the DHCP server. This might indicate that scope lease durations are too short.

Nacks/sec

The number of DHCP negative acknowledgment messages (DHCPNAKs) sent per second by the DHCP server to clients. A very high value might indicate potential network trouble in the form of an incorrect configuration of either the server or clients. When servers are incorrectly configured, one possible cause is a deactivated scope. For clients, a very high value can be caused by computers moving between subnets, such as laptops or other mobile devices.

Declines/sec

The number of DHCP decline messages (DHCPDECLINEs) received per second by the DHCP server from clients. A high value indicates that several clients have found their address to be in conflict, possibly indicating network trouble. In this situation, it can help to enable conflict detection on the DHCP server. This should only be used temporarily. After the situation returns to normal, it should be turned off. For more information, see Enable IP Address Conflict Detection.

Releases/sec

The number of DHCP release messages (DHCPRELEASEs) received per second by the DHCP server from clients. This number only exists if a DHCP client sends a release to the server. This can occur manually, such as when the ipconfig command is used at the client computer. Release messages can also be sent by the client if it is configured with the "Release DHCP lease on shutdown" option. Because clients rarely release their address, the value of this counter remains low for many DHCP network configurations.

A member of the local Administrators group can change values stored at the following registry path location to deny or modify permissions that determine who can view System Monitor counters used for the DHCP server on the server computer. Values under this key are used by the System Monitor DLL (Perfctrs.dll) to identify each of the counters described.

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\DHCPServer\Performance

CautionCaution
Incorrectly editing the registry can severely damage your system. Before making changes to the registry, you should back up any valued data on the computer.

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