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Managing and Monitoring DHCP

After a DHCP server has been installed, it most certainly must be maintained. This entails performing management tasks and monitoring the server on a regular basis to ensure adequate performance over time. A number of tools are available that you can use to perform these tasks, including:

  • DHCP Manager for managing the DHCP service

  • System Monitor for monitoring real-time performance of a DHCP server

  • Event Viewer for viewing any messages generated by the DHCP service

  • Network Monitor for monitoring DHCP-related network traffic

Using the DHCP Manager

As you've seen throughout this chapter, the DHCP Manager is where most DHCP server-management tasks are performed.

The Action menu within the management console has a number of options. Some of the options are outlined in the next section beginning with “Displaying Statistics.”

Displaying Statistics

When you highlight the DHCP server and choose Display Statistics from the Action menu, the Server Statistics dialog box opens (see Figure 3.10), providing you with a summary of what is happening on the server.

03fig10.jpgFigure 3.10. Viewing DHCP server statistics.

The statistics window displays the following items:

  • Start Time — The time when the service was last started

  • Up Time — Length of time since the service was last restarted

  • Discovers — The number of DHCPDISCOVER messages received by the server

  • Offers — The number of offers the DHCP server has sent out

  • Requests — The number of DHCPREQUEST messages received by the server

  • Acks — The number of acknowledgements the server has sent out

  • Nacks — The number of negative acknowledgements the server has sent out

  • Declines — The number of decline messages the server has sent out

  • Releases — The number of release messages the server has received

  • Total Scopes — The number of scopes that are currently active on the server

  • Total Addresses — The number of IP addresses the server has available for lease to DHCP clients

  • In Use — The number of IP addresses currently leased to clients

  • Available — The number of IP addresses left in the pool

Reconciling Scopes

The Reconcile All Scopes option is useful when you need to fix any inconsistencies in the DHCP database, such as when not all IP address leases are being reflected in the DHCP database. Information in the database is compared with information stored in the Registry.

Selecting the Reconcile All Scopes option opens the Reconcile All Scopes dialog box. Click the Verify button to check the database for inconsistencies. Any errors are displayed (see Figure 3.11).

03fig11.jpgFigure 3.11. Checking the DHCP database for inconsistencies.

Other Management Tasks in the DHCP Manager Action Menu

You can also perform a number of other tasks from the Action menu, including

  • Unauthorize — Use this option to unauthorize a DHCP server. The server will no longer appear in the list of authorized servers within Active Directory.

  • Start/Stop — Use these options to stop and start the DHCP Server service.

  • Pause/Resume — Use these options to pause and resume the DHCP server.

  • Restart — Use this option to restart the DHCP Server service. Doing so resets all the server statistics discussed earlier.

Note

The last three options described in the preceding list can be found under the All Tasks menu option.

Finally, selecting the Properties option from the Action menu opens the Properties dialog box for the DHCP server. The Properties dialog box contains three tabs:

  • General

  • DNS

  • Advanced

You have already seen the DNS tab earlier in the chapter; the next two sections cover the other two tabs in further depth.

The General Tab

On the General tab, you can configure how often the statistics gathered for the server are refreshed (see Figure 3.12), whether to write DHCP information to the System log within Event Viewer, and whether to display the BOOTP configuration information in the DHCP management console.

03fig12.jpgFigure 3.12. Configure DCHP server properties.

The Advanced Tab

On the Advanced tab (see Figure 3.13), you can configure conflict detection, which specifies the number of times the DHCP server should attempt to determine whether an IP address is already in use before assigning it to a DHCP client. You can also change the location of the DHCP database and audit log, as well as check the connections used to service DHCP clients.

03fig13.jpgFigure 3.13. Configuring the Advanced properties of a DHCP server.

Tools for Monitoring

It's always good practice to monitor server performance, whether it's a DHCP server, a domain controller, or a DNS server. Windows 2000 comes with a number of tools that can be used to monitor different aspects of a DHCP server. The following section looks at monitoring real-time performance of a DHCP server, logging DHCP related events, and monitoring DHCP related traffic.

System Monitor

The tool most commonly used for monitoring is the System Monitor found in the Performance MMC within the Administrative Tools menu. Once the DHCP Server service is installed, a number of counters are added that allow you to monitor specific aspects of DHCP (see Figure 3.14). Some of the more commonly used counters include:

  • Packets Received/Sec — Monitors the rate at which packets are received by the DHCP server. This counter monitors all request types received by the server.

  • Requests/Sec — Monitors the rate at which DHCP requests are received by the DHCP server. If this value is high, consider increasing the lease duration.

  • Offers/Sec — Monitors the rate at which offers are sent by the DHCP server.

  • Releases/Sec — Monitors the rate at which releases are received by the DHCP server.

  • Active Queue Length — Monitors the number of packets in the processing queue of the DHCP server.

  • Conflict Check Queue Length — Monitors the number of packets in the DHCP server queue waiting on conflict detection.

03fig14.jpgFigure 3.14. DHCP performance counters.

Event Viewer

If the DHCP server is configured to log activity, you can use the System Log within the Event Viewer to monitor and troubleshoot events. When an event does occur, such as the DHCP Server service being restarted, it is written to the log file and provides useful information, including a description of the event and when it occurred.

Network Monitor

Network Monitor is a “sniffer” that can be used to capture network traffic coming to and from a computer. In terms of DHCP, you can use it to view and analyze traffic between a DHCP server and DHCP clients, such as the IP address lease process.

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