Dynamic Host Configuration Protocol

Monitoring Server Performance

Because DHCP servers are of critical importance in most environments, monitoring the performance of servers can help in troubleshooting cases where server performance degradation occurs.

For Windows 2000 Server, the DHCP service includes a set of performance counters that can be used to monitor various types of server activity. By default, these counters are available after the DHCP service is installed. To access these counters, you must use System Monitor (formerly Performance Monitor). The DHCP server counters can monitor:

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 on the DHCP server computer.

DHCP System Monitor Counters

Table 4.13 provides a list of the DHCP system monitor counters and their meaning:

Table 4.13 DHCP System Monitor 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. A large number indicates clients are probably timing out too fast or the server is not responding very fast.
Packets Expired/sec	The number of packets per second that expire and are dropped by the DHCP server. Packets expire because they are in the server's internal message queue for too long. A large number here indicates that the server is either taking too long to process some packets while other packets are queued, or traffic on the network is too high for the DHCP server to handle.
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 unreasonable increase may indicate trouble, possibly with the I/O subsystem getting slower or because of some intrinsic 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 may indicate heavy server traffic.
Conflict Check Queue Length	The current length of the conflict check queue for the DHCP server. This queue holds messages not responded to while the DHCP server performs address conflict detection. A large value here may indicate heavy lease traffic at the server or that Conflict Detection Attempts has been set too high.
Discovers/sec	The number of DHCPDiscover messages received per second by the server. A sudden or abnormal increase indicates that a large number of clients are probably attempting to initialize and obtain an IP address lease from the server, such as when a number of client computers are started at one time.
Offers/sec	The number of DHCPOffer messages sent per second by the DHCP server to clients. A sudden or abnormal increase in this number indicates heavy traffic on the server.
Requests/sec	The number of DHCPRequest messages received per second by the DHCP server from clients. A sudden or abnormal increase in this number indicates that a large number of clients are probably trying to renew their leases with the DHCP server. This may indicate scope lease times are too short.
Informs/sec	The number of DHCPInform messages received per second by the DHCP server. DHCPInform messages are used when the DHCP server queries the directory service for the enterprise root and when dynamic updates are being done on behalf of clients by the DNS server.
Acks/sec	The number of DHCPAck messages sent per second by the DHCP server to clients. A sudden or abnormal increase in this number indicates that a large number of clients are being renewed by the DHCP server. This may indicate scope lease times are too short.
Nacks/sec	The number of DHCP negative acknowledgment messages sent per second by the DHCP server to clients. A very high value might indicate potential network trouble, either misconfiguration of clients or the server. Where servers can be misconfigured, one possible cause is a deactivated scope. For clients, a very high value could be caused by computers (such as laptop portables or other mobile devices) moving between subnets.
Declines/sec	The number of DHCPDecline messages 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 may help to enable conflict detection on the DHCP server. If used on the server, conflict detection should only be used temporarily. Once the situation returns to normal, it should be turned off.
Releases/sec	The number of DHCPRelease messages received per second by the DHCP server from clients. This number is only generated when clients manually release their address, such as when the ipconfig /release command is used at the client computer. Because clients rarely release their address, this counter should not be high for most networks and configurations.