Lesson Managing a DHCP Database

* Overview of Managing DHCP

* What Is a DHCP Database?

* How a DHCP Database Is Backed Up and Restored

* How To Back Up and Restore a DHCP Database

* How a DHCP Database Is Reconciled

* How To Reconcile a DHCP Database

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Introduction

Lesson objectives

It is important to protect your DHCP database, manage the growth of your DHCP database, and ensure DHCP database consistency. This can be accomplished by backing up, restoring, and reconciling the DHCP database.

After completing this lesson, you will be able to:

■ Explain the purpose of managing DHCP.

■ Explain what a DHCP database is.

■ Describe how a DHCP database is backed up and restored.

■ Back up and restore a database.

■ Describe how a DHCP database is reconciled.

■ Reconcile a DHCP database.

■ Manage a DHCP database.

Overview of Managing DHCP

The DHCP service needs to be managed to reflect changes in the network and the DHCP server

Scenarios for managing DHCP:

Managing DHCP database growth

* Protecting the DHCP database

Ensuring DHCP database consistency

t Adding clients

Adding new network service servers

< Adding new subnets

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Why manage a service? After a service is installed, consideration must be given to the steps that are required to manage and maintain the service so that it continues to provide the services that clients require over time. When you configure a network service, you are solving a network issue at a given point in time. Because the network environment can change, you need to monitor the service and, potentially, to modify the solution to keep it current.

Why manage the DHCP You need to manage the DHCP service to reflect changing client IP addressing service? needs. Client IP addressing needs can change if new clients, new subnets, or new servers are added to or subtracted from the network.

You also need to manage the DHCP service to respond to changing DHCP server conditions, and to protect the DHCP database from failure.

Scenarios for managing The following table lists common scenarios in which an administrator would DHCP manage DHCP. Also listed are the corresponding tasks and tools for managing

DHCP.

Scenarios

Tasks

Tools for managing DHCP

Managing DHCP database Compact the DHCP

growth

Protecting the DHCP database database

Back up and restore the DHCP database

Ensuring DHCP database Reconcile DHCP scopes consistency

Adding clients

Adding new network service servers

Adding new subnets

Jetpack.exe DHCP console DHCP console DHCP console DHCP console

Configure or modify scopes

Configure or modify options

Configure the DHCP relay DHCP console agent

Note This module only covers how to manage a DHCP database. Because the procedural steps for managing scopes, options, and DHCP relay agents are similar to the procedural steps for configuring scopes, options, and DHCP relay agents, you can refer to Module 2, "Allocating IP Addressing by Using Dynamic Host Configuration Protocol (DHCP)" in Course 2277, Implementing, Managing, and Maintaining a Microsoft® Windows® Server 2003 Network Infrastructure: Network Services.

What Is a DHCP Database?

Dhcp Database Agent

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Definition

Purpose of a DHCP database

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The DHCP database is a dynamic database that is updated when DHCP clients are assigned or as they release their Transmission Control Protocol/Internet Protocol (TCP/IP) address leases.

The DHCP database contains the DHCP configuration data (such as information about scopes, reservations, options, leases, etc.). The DHCP service will not start without the database.

Where a DHCP database Windows Server 2003 stores the DHCP database in the directory is stored

%sytemroot%\System32\Dhcp. By default, the database is automatically backed up to the Backup\New directory, which is located in the database directory.

DHCP files The DHCP database is made up the following files, which are stored in the

\%Systemroot%\System32YDhcp directory.

File Description

DHCP.mdb The database file for the DHCP service. The file contains two tables: the IP-address-Owner-ID mapping table and the name-to-IP address mapping table.

Tmp.edb A temporary file that the DHCP database uses as a swap file during database index maintenance operations.

J50.log and J50*.log Logs of all transactions that are made with the database.

DHCP uses these logs to recover data, if necessary.

Res*.log Reserved log files that are used to record the existing transactions if the system runs out of disk space.

J50.chk A checkpoint file.

Caution Do not tamper with or remove any of these files. The DHCP service will not load without these files, so if you make any changes to them you risk failure of your DHCP server.

How a DHCP Database Is Backed Up and Restored

In the event that the server hardware fails, the administrator can restore only from the offline storage location

Why back up and restore a DHCP database?

How a DHCP database is automatically backed up

How a DHCP database is manually backed up

How a DHCP database is restored

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To provide fault tolerance in the case of a failure, it is important to back up the DHCP database. This will enable you to restore the database from the backup copy if the hardware fails.

By default, the DHCP service automatically backs up the DHCP database and related registry entries to a backup directory on the local drive every 60 minutes. By default, automatic backups are stored in the \%S>wfeOTroo?%\System32\Dhcp\Backup\New directory. The administrator can change the backup location.

The administrator can then copy the backed up DHCP files to an offline storage location (such as a tape or a disk).

You can also back up the DHCP database manually. By default, manual backups are stored in the \0%>'sfeOTroo?%\System32\Dhcp\Backup\New directory. The administrator can change the backup location.

When the DHCP service starts, if the original DHCP database is unable to load, then the DHCP service automatically restores to a backup directory on the local drive.

In the event that the DHCP database fails, the administrator can choose either to restore from the backup directory on the local drive or to restore from the offline backup location.

In the event that the server hardware fails and the local backup is unavailable, the administrator can only restore from the offline backup location.

How to Back Up and Restore a DHCP Database

Your instructor will demonstrate how to:

*> Apply guidelines when backing up and restoring a DHCP database

* Configure a DHCP database backup path

* Manually back up a DHCP database to the backup directory on a local drive

Manually restore a DHCP database from the backup directory on a local drive

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Introduction If you cannot repair the database by using Jetpack.exe, you can restore the database from the backup directory on the local drive. If restoring the DHCP database from the backup directory on the local drive is unsuccessful, you must restore the DHCP database from an offline storage location.

Even though you can both automatically and manually back up and restore a DHCP database to and from a backup directory on the local drive, you can only manually back up and restore a DHCP database to and from an offline storage location.

Note It is recommended that you log on with an account that has nonadministrative credentials and use the Run as command with a user account that has appropriate administrative credentials to perform this task.

Guidelines When backing up and restoring a DHCP database, apply the following guidelines.

■ Manually back up the DHCP database to a location other than %S>wfeOTroo?%\System32YDhcpYBackup\JetYNew, which is the default location for the automatic backup. If you store a manually created copy of the DHCP database in the same location as the copy that was created automatically, the DHCP service will not function properly.

■ Maintain a copy of the backed up DHCP database offline (for example, on a tape or a disk). Because the DHCP service automatically backs up a copy of the DHCP database to a location on the local drive, you lose both the original DHCP database and the backup DHCP database if the hardware fails.

Procedure for configuring a DHCP database backup path

Procedure for manually backing up a DHCP database to the backup directory on a local drive

Procedure for manually restoring a DHCP database from the backup directory on a local drive

To configure a DHCP database backup path:

1. In the DHCP console, in the console tree, select the appropriate DHCP server.

2. On the Action menu, click Properties.

3. On the Advanced tab, in the Backup path field, type the appropriate backup path and then click OK.

To manually back up a DHCP database to the backup directory on a local drive:

1. In the DHCP console, in the console tree, select the appropriate DHCP server.

2. On the Action menu, click Backup.

3. In the Browse For Folder dialog box, select the appropriate folder to back up to, and then click OK.

To manually restore a DHCP database from the backup directory on a local drive:

1. In the DHCP console, in the console tree, select the appropriate DHCP server.

2. On the Action menu, click Restore.

3. In the Browse For Folder dialog box, select the folder where the backup resides and then click OK.

4. In the DHCP dialog box, click Yes to stop and then restart the service.

5. If the status of the service doesn't update, refresh the DHCP console.

Note For more information about how to manually back up and restore a DHCP database to and from an offline storage location, refer to Course 2275, Maintaining a Microsoft Windows Server 2003 Environment.

DHCP Server

Compares information to find inconsistencies

Reconciles inconsistencies in the DHCP database

Example

Summary information

Detailed information

Reconciled DHCP database

Client has IP address

IP address 192.168.1.34

Create an active lease entry

192.168 1,34

is available

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Definition Reconciling is the process of verifying DHCP database values against DHCP

registry values.

When to reconcile a It is recommended that you reconcile your DHCP database: DHCP database

■ When the DHCP database values are configured correctly, but are not displayed correctly in the DHCP console.

■ After you have restored a DHCP database, but the restored DHCP database does not have the most recent values.

For example: your existing database is deleted, and you must restore an older version of the database. If you start DHCP and open the console, you will notice that the scope and options display, but the active leases do not. Reconciling populates the client lease information from the registry to the DHCP database.

How a DHCP database is When you reconcile a server or a scope, the DHCP service uses both the reconciled summary information in the registry and the detailed information in the DHCP

database to reconstruct the most current view of the DHCP service.

For example: after a DHCP database is restored, an active lease is not displaying in the DHCP console The process of reconciliation will verify the summary information for that address lease in the registry with the detailed information in the DHCP database. The summary information shows that a client has the IP address, but the detailed information shows that the IP address is available. After the information between the registry and the database is compared, the DHCP database is updated with this active lease information. The active lease will then display in the DHCP console.

How to Reconcile a DHCP Database in. „..,1.. M M WI^M ■—■ 1 B^w—

Your instructor will demonstrate how to:

♦ Prepare to reconcile a DHCP database

*> Reconcile all scopes in a DHCP database

* Reconcile a scope in a DHCP database

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Introduction

Preparing to reconcile

Procedure for reconciling all scopes in a DHCP database

You can choose to reconcile all scopes on the server by selecting the DHCP server, or you can reconcile one scope by selecting the appropriate scope.

Note It is recommended that you log on with an account that has nonadministrative credentials and use the Run as command with a user account that has appropriate administrative credentials to perform this task.

Before using the Reconcile feature to fully recover client information for a DHCP scope from the registry, the server computer needs to meet the following criteria.

■ All DHCP server registry keys must either be restored, or exist and remain intact from previous service operations on the server computer.

■ A new version of the DHCP server database file must be generated in the %Systemroot%\System32\Dhcp folder on the server computer.

When the registry and database meet the previous criteria, you can restart the DHCP service. At this point, upon opening the DHCP console, you might notice that scope information is present, but that there are no active leases displayed. To regain your active leases for each scope, you use the Reconcile feature to recover each scope.

To reconcile all scopes in a DHCP database:

1. In the DHCP console, in the console tree, select the DHCP server.

2. On the Action menu, click Reconcile All Scopes.

3. In the Reconcile All Scopes dialog box, click Verify.

4. In the DHCP dialog box, click OK.

Procedure for To reconcile a scope in a DHCP database:

reconciling a scope in a

DHCP database 1. In the DHCP console, select the appropriate scope in the console tree.

Note You can choose to reconcile one scope by selecting the appropriate scope, or reconcile all scopes on the server by selecting the DHCP server.

2. On the Action menu, click Reconcile.

3. In the Reconcile dialog box, click Verify.

4. In the DHCP dialog box, click OK.

After reconciling After using the Reconcile feature, when viewing properties for individual clients that are shown in the list of active leases, you might notice that client information is displayed incorrectly. This information is corrected and updated in DHCP Manager as scope clients renew their leases.

Practice: Managing a DHCP Database

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In this practice, you will manage a DHCP database

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Objective Instructions

Scenario Practice

In this practice, you will manage a DHCP database.

You must be logged on with an account that has non-administrative credentials and use the Run as command with a user account that has appropriate administrative credentials to complete the task.

The systems engineer has decided to run some tests against the DHCP server hardware in the Lab department. You need to manually back up the DHCP database. After the test has been run on the DHCP server, you will reconcile the server to ensure that the DHCP server database is correct.

► Configure the DHCP database backup path

■ Complete this task from both student computers.

■ Backup path: C:\Moc\2277\Labfiles\Lab03

► Manually back up a DHCP database to the backup directory on a local drive

■ Complete this task from both student computers.

■ Backup path: C:\Moc\2277\Labfiles\Lab03\Manual Backup

► Manually restore a DHCP database from the backup directory on a local drive

■ Complete this task from both student computers.

■ Restore path: C:\Moc\2277\Labfiles\Lab03\Manual Backup

► Reconcile all scopes in a DHCP database

■ Complete this task from both student computers.

■ Reconcile all scopes.

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Responses

  • Steven Carson
    What is managing dhcp database?
    3 years ago
  • willow
    How to reconcile backup?
    1 year ago
  • aretha hanson
    Why is is important to backup the dhcp database?
    9 months ago
  • welde tewelde
    What is the windows command to obtain and managing dhcp tasks?
    8 months ago
  • Heikki
    How to reconcile a dhcp database?
    6 months ago
  • joshua
    Why is it important to back up a dhcp server?
    6 months ago
  • aamos ketola
    What information is stored in a DHCP server?
    5 months ago
  • CHRISTIN
    What is stored in a dhcp database?
    5 months ago
  • monika wechsler
    What ius the risk of changing dhcp entries overnight?
    4 months ago
  • Ted Maggot
    What is dhcp database file extension?
    4 months ago

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