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PSS ID Number: Q173396
Article last modified on 11-28-2001

:2000,3.51,4.0




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The information in this article applies to:

- Microsoft Windows NT Server versions 3.51, 4.0
- Microsoft Windows 2000 Server
- Microsoft Windows 2000 Advanced Server
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IMPORTANT: This article contains information about editing the registry.
Before you edit the registry, make sure you understand how to restore it if
a problem occurs. For information about how to do this, view the "Restoring
the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help
topic in Regedt32.exe.

SUMMARY
=======

This article discusses methods that may be used to recover a corrupted Dynamic
Host Configuration Protocol (DHCP) database.

MORE INFORMATION
================

WARNING: Using Registry Editor incorrectly can cause serious problems that may
require you to reinstall your operating system. Microsoft cannot guarantee that
problems resulting from the incorrect use of Registry Editor can be solved. Use
Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and
Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete
Information in the Registry" and "Edit Registry Data" Help topics in
Regedt32.exe. Note that you should back up the registry before you edit it. If
you are running Windows NT or Windows 2000, you should also update your
Emergency Repair Disk (ERD).

The following event log messages appear on a computer running Windows NT Server
versions 3.51 and 4.0 when the DHCP database has been corrupted:

Event ID: 1014
Source: DhcpServer
Description: The Jet database returned the following Error: -510.

-or-

Event ID: 1014
Source: DhcpServer
Description: The Jet database returned the following Error: -1022.

-or-

Event ID: 1014
Source: DhcpServer
Description: The Jet database returned the following Error: -1850.

If you use Jet.exe to compact the DHCP database, you will not resolve the issue.

For additional information, click the article number below to view the article in
the Microsoft Knowledge Base:

Q153476 DHCP Stops Assigning IP Addresses to Clients

The DHCP database is contained in the Dhcp.mdb file located in the
%SystemRoot%\\System32\\Dhcp folder. The DHCP server uses this file to record and
store information concerning active leases and reservations. Most of this
information is also contained in the following registry key:

HKEY_LOCAL_MACHINE\\System\\CurrentControlSet\\Services
\\DHCPServer\\Configuration

NOTE: The above registry key is one path; it has been wrapped for readability.

Whenever the DHCP service shuts down correctly, it makes a backup copy of both
the database file (Dhcp.mdb) and the registry key. The backup information from
the registry is contained in the file Dhcpcfg. For Windows NT 3.51, the file
Dhcp.mdb is located in the %SystemRoot%\\System32\\Dhcp\\Backup\\Jet folder. In
Windows NT 4.0, the file Dhcp.mdb is located in the
%SystemRoot%\\System32\\Dhcp\\Backup\\Jet\\New folder. Both versions of Windows NT
store the Dhcpcfg file in the %SystemRoot%\\System32\\Dhcp\\Backup folder.

To recover a corrupted DHCP database, use one of the following methods:

- Restore a backup copy of the database file, Dhcp.mdb

- or-

- Generate a new database file using the DHCP Configuration registry key.

Restoring a backup copy of the database file is the recommended method because
you will not lose information when you use it.

After you recover your database file using one of the methods above, you will
need to reconcile the information between the database file and the registry
information.

NOTE: The following steps assume that your DHCP server will not start because of
a corrupted DHCP database. If your DHCP server starts, but the database is
corrupted, you will then need to begin by stopping the service.

To stop the DHCP server service, type the following at a command prompt:

net stop dhcpserver

Restoring a Backup Copy of the Database
---------------------------------------

1. Move the files from your existing DHCP folder to a different location, being
careful to keep the DHCP folder structure intact. For example, type the
following at a command prompt and press ENTER after each line:

md c:\\Olddhcp
move %SystemRoot%\\system32\\DHCP\\*.* C:\\Olddhcp

2. Remove the corrupted database file.

3. Copy the backup database file into the DHCP folder by typing the following at
a command prompt, and then pressing ENTER:

Windows NT 3.51:

copy %SystemRoot%\\system32\\dhcp\\backup\\jet\\dhcp.mdb
%SystemRoot%\\system32\\dhcp\\dhcp.mdb

Windows NT 4.0:

copy %SystemRoot%\\system32\\dhcp\\backup\\jet\\new\\dhcp.mdb
%SystemRoot%\\system32\\dhcp\\dhcp.mdb

NOTE: The above command lines are continuous lines; they have been wrapped for
readability.

You may also choose to restore the Dhcp.mdb file to the
%SystemRoot%\\System32\\Dhcp folder from a tape backup or other backup media.

Because you are using an existing database file, whether you restore it from
backup media or the backup folder, you should compress it using the Jetpack
utility.

For additional information, click the article number below to view the article in
the Microsoft Knowledge Base:

Q145881 How to Use Jetpack.exe to Compact a WINS or DHCP Database

The procedure above should allow the service to start, but if your scope
information is missing it may be necessary to use a backup copy of the Dhcpcfg
registry file to restore your scope and reservation information. Refer to steps
5 through 11 in the "From the New DHCP Server" section of the following
article:

For additional information, click the article number below to view the article in
the Microsoft Knowledge Base:

Q130642 How to Move a DHCP Database to Another Windows NT Server

Generating a New Database File
------------------------------

1. Move the files in your existing DHCP folder to a different location, being
careful to keep the DHCP folder structure intact. For example, type the
following at a command prompt, pressing ENTER after each line:

md c:\\olddhcp
move %SystemRoot%\\system32\\dhcp\\*.* c:\\olddhcp

2. Select the next step from the following list, depending on which version of
Windows NT Server you are using:

Windows NT Server 3.51:

Expand a new copy of System.mdb from the original Windows NT Server source
media by inserting your original Windows NT Server 3.51 CD into your CD-ROM
drive. To do so, type the following at a command prompt, and then press
ENTER:

expand D:\\I386\\System.md_ %SystemRoot%\\System32\\Dhcp\\System.mdb

where D: is your CD-ROM drive and i386 is your platform.

Windows NT Server 4.0:

Restart the DHCP server with an empty DHCP folder. Windows NT 4.0 and Windows
2000 do not use a System.mdb file.

The procedure above should allow the service to start, but if your scope
information is missing, it may be necessary to use a backup copy of the Dhcpcfg
registry file to restore your scope and reservation information. Refer to steps
5 through 11 in the "From the New DHCP Server" section of the following
article:

For additional information, click the article number below to view the article in
the Microsoft Knowledge Base:

Q130642 How to Move a DHCP Database to Another Windows NT Server

Reconciling DHCP Information
----------------------------

After you generate a new database file, you may notice that the scope information
is present, but no active leases are displayed. To regain the active leases, you
need to reconcile the database with the information in the registry using the
following steps:

1. From DHCP Manager, click your scope, and then click Active Leases on the
Scope menu.

2. In the Active Leases dialog box, click Reconcile.

3. Click OK. Your active leases will appear in the Active Leases dialog box.

NOTE: When you view the properties for a client lease, the computer name will be
listed as the IP address of the lease and an arbitrary hexadecimal value will be
listed as the client identifier. These will be replaced with the appropriate
information as the clients renew their leases.

Repeat the above procedure for each scope for which you need to reconcile
leases.

If your DHCP server is Windows NT Server 4.0 SP2 or later, you should enable IP
Conflict Detection as described in the following article:

Q161430 Detecting and Flagging Duplicate IP Addresses

Additional query words:

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Keywords : kbnetwork
Technology : kbWinNTsearch kbWinNT351search kbWinNT400search kbwin2000AdvServ kbwin2000AdvServSearch kbwin2000Serv kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbWinNTS351 kbwin2000ServSearch kbwin2000Search kbWinNTS351search kbWinAdvServSearch
Version : :2000,3.51,4.0
Issue type : kbhowto
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Copyright Microsoft Corporation 2001.