DHCP Server Management and Monitoring
- Manage DHCP databases.
We have spent some time now examining the installation and configuration of the Windows Server 2003 DHCP service. The final piece of the DHCP puzzle is managing and monitoring the server after it is installed and configured. The Windows Server 2003 DHCP server bundles enhanced monitoring and statistical reporting for precisely that purpose.
The DHCP console has several features that can be accessed by selecting the server and clicking the Action menu or by right-clicking the server. We examine these management and monitoring features in more detail in the following sections.
Examining the DHCP Server Statistics
The Display Statistics command opens the Server Statistics window, which is shown in Figure 2.34.
Figure 2.34 The Server Statistics window quickly displays pertinent DHCP statistics.
The Server Statistics window displays the following statistics:
- Start Time—The date and time the service was started.
- Up Time—The total uptime for the DHCP service. If you restart the service, this number resets to zero, even if the DHCP server has not been restarted.
- Discovers—The number of DHCPDISCOVER packets the server has received.
- Offers—The number of DHCPOFFER packets the server has sent.
- Requests—The number of DHCPREQUEST packets the server has received.
- Acks—The number of DHCPACK packets the server has sent.
- Nacks—The number of DHCPNACK packets the server has sent.
- Declines—The number of DHCPDECLINE packets the server has received.
- Releases—The number of DHCPRELEASE messages the server has received.
- Total Scopes—The total number of scopes that are active on the server.
- Total Addresses—The total number of addresses available. This number includes the number of addresses for all the active scopes on the server.
- In Use—The number of addresses presently leased to DHCP client computers.
- Available—The number of addresses available for lease for the total address pool.
DHCP Server Backup and Restore
As mentioned earlier in this chapter, DHCP server backup and restore is one of the new features found in the DHCP service in Windows Server 2003. Two types of backups from the DHCP console are supported:
Synchronous—A synchronous backup occurs automatically on the configured interval. The default interval is 60 minutes and can be changed from the registry location HKEY_LOCAL_MACHINE\SYSTEM\
- Asynchronous—An asynchronous backup is a manual backup that is performed by using the Backup command from within the DHCP console.
Both types of DHCP backups place their data in the same location, which is %systemroot%\System32\Dhcp\Backup by default. You can then use Windows Backup (NTBACKUP.exe) or any other backup application to safely back up this data to another location. You can change the database backup folder by selecting a different local folder during a manual backup or by changing the backup folder location in the DHCP server properties.
Backups of the DHCP data from the DHCP console include the following items:
- All scopes
- All reservations
- All leases
- All options, including server options, scope options, reservation options, and class options
- All registry data in the following registry location: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCPServer\Parameters
You can manually perform a backup by selecting Action, Backup. In addition, you can perform the restoration of the DHCP data by selecting Action, Restore. If you want to change the backup path, you can do so from the Advanced tab of the DHCP Server Properties dialog box.
Reconciling the DHCP Database
- Verify database integrity.
When you reconcile scopes on your DHCP server, you are comparing the information contained in the DHCP database against the information stored in the registry. Typically, reconciliation of scopes is performed when you are observing problems with the DHCP server and want to verify the configured addresses. The Reconcile All Scopes command allows you to perform this comparison should you need to. You can click the Verify button in the Reconcile All Scopes dialog box (shown in Figure 2.35) to check the consistency of the database and get a report of any errors.
Figure 2.35 You can reconcile all scopes from the Reconcile All Scopes dialog box.
Stopping the DHCP Server
Sometimes you'll want to prevent a DHCP server from giving out leases so that you can perform maintenance on the server or make configuration changes to scopes on the server. You can cause this happen by either unauthorizing the server or by stopping the DHCP server service. The Unauthorize command removes the DHCP server from the list of authorized DHCP servers in Active Directory. You are warned before removal occurs, as shown in Figure 2.36.
Figure 2.36 Unauthorizing a DHCP server prevents it from servicing client requests.
The advantage of unauthorizing a server versus stopping the DHCP server service, as shown in Figure 2.37, is that you can still perform scope and server configuration and modification while the server is unauthorized. That is not possible when the DHCP server service has been stopped on the server.
Figure 2.37 Stopping the DHCP server service removes the ability to perform configuration on it.
Configuring Options and Classes
The options Define User Classes, Define Vendor Classes, and Set Predefined Options are beyond the scope of Exam 70-291. You will probably not use them in the context of a standard DHCP installation, but you should be aware of what user classes and vendor classes are in general so that your knowledge of DHCP will be complete.
- User classes—User classes are generally created for administrative purposes, similar to user groups. They can be used to identify all the DHCP clients in a specific department or location. User classes are used to assign DHCP options to groups of DHCP clients.
- Vendor classes—Vendor classes are generally used to provide vendor-specific DHCP enhancements. For example, the Windows Server 2003 DHCP service has the capability to disable NetBT on its DHCP clients.
Changing the Server State
Should you want to change the state of the server, perhaps pause or stop the DHCP server altogether, you can do this from the Action menu. Selecting Action, All Tasks opens a submenu that allows you to control the operational state of the DHCP server. The following options are available:
- Start—Starts the DHCP service. This option is available only if the service is stopped or paused.
- Stop—Stops the DHCP service. This option is available when the service is running or paused. This option causes the server statistics to be reset.
- Pause—Pauses the DHCP service. This option does not reset the statistics.
- Resume—Resumes the DHCP service after it is paused. This option is available only when the service is paused.
- Restart—Restarts the DHCP service, resetting the server statistics in the process. This option is available only if the service is currently running.
DHCP Server Common Commands
The three commands Delete, Refresh, and Export List are common ones. The Delete command deletes the DHCP server. The Refresh command causes all the displayed information to be refreshed with a current status. The Export List command allows you to export the information displayed in the right pane of the console window to a tab- or comma-delimited text or Unicode text file. You can export a list of various nodes by clicking them before selecting the Export List command.
The Properties command opens the Properties dialog box for the selected DHCP server. The Properties dialog box (shown previously in Figure 2.33) opens to the General tab, which allows you to configure the following options.
- Automatically Update Statistics Every—This option allows you to set the automatic refresh of the statistics, as well as the interval at which the statistics are refreshed.
- Enable DHCP Audit Logging—This option allows you to log all the DHCP activity to a text file located in the %systemroot%\System32\dhcp folder, which can be opened in Notepad or any other text editor. This is an excellent option to select if you are troubleshooting a DHCP problem and want to see what activity is taking place on the server.
- Show the BOOTP Table Folder—This option deals with BOOTP backward compatibility and allows you to view the table that contains the BOOTP configuration entries. After you select this option, the BOOTP Table node appears in the DHCP console, as shown in Figure 2.38. From this node you can configure boot images for BOOTP clients. Remember, however, that you still need to provide your own third-party TFTP server.
Figure 2.38 When the BOOTP Table folder is enabled, you can perform configuration of BOOTP boot images.
The DNS tab of the Properties dialog box is discussed in detail earlier in this chapter, in the section "Configuring DHCP for DNS Integration." You can use the Advanced tab, shown in Figure 2.39, to perform more advanced and less common configuration tasks.
The Advanced tab has the following configuration options:
- Conflict Detection Attempts—This option causes the DHCP server to check for conflicting IP addresses on the network before issuing an address. Although this sounds like a great way to make sure there are no address conflicts, it can add significant overhead to the server, and you should use it only while you're troubleshooting address conflict issues. By default, this option is set to 0.
- Audit Log File Path—If audit logging is enabled, the log file is located in the %systemroot%\System32\dhcp directory. You can modify the location to be any location on the local computer (including mapped drives).
Database Path—This option allows you to specify the location of the DHCP database. By default, it is in the %systemroot%\System32\dhcp directory. You can modify the location to be any location on the local computer (including mapped drives).
Figure 2.39 The Advanced tab contains all the options that don't fit anywhere else.
- Backup Path—This option allows you to specify the location of the DHCP backup file. By default, it is in the %systemroot%\System32\dhcp\backup directory. You can modify the location to be any location on the local computer (including mapped drives).
Change Server Connection Bindings—This option allows you to view the connections through which the DHCP server is providing addresses. If you have multiple network adapters in a DHCP server, you might want to configure DHCP for only selected interfaces. You can click the Bindings button to view and configure the binding on your computer, as shown in Figure 2.40.
Figure 2.40 You can view and change the DHCP bindings from the Bindings window.
- DNS Dynamic Updates Registration Credentials—As discussed previously, this option allows you to specify a domain user account to be used during DNS dynamic updates.