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LabMice Tip

How to get the most out of your DHCP Servers:

The easiest way to improve DHCP Server Performance is by improving Disk I/O
DHCP servers usually choke on the disk read/write operations, rather than processor utilization or memory. Always use the fastest drives and controllers you can afford for DHCP servers.

Use less than 1,000 scopes per Server.
Every scope that resides on a DHCP server requires additional disk space for the DHCP registry and paging file. Large scopes require more disk operations and will slow your systems.

Limit 10,000 clients per server.
There is no fixed limit to the number of clients that a DHCP server can accommodate, but as a general rule try to limit your DHCP servers to no more than 10,000 clients. This will give them a little breathing room when all of your clients try to log in at once.

	DHCP (Dynamic Host Configuration Protocol)
For any Administrator who's ever had to maintain a large network with static IP address's, DHCP (Dynamic Host Configuration Protocol) is a godsend. But there are a few pitfalls if you don't configure it correctly, and troubleshooting can be a nightmare if you don't really understand how it works.

Where to start.....

DHCP (Dynamic Host Configuration Protocol) Basics
Microsoft Knowledge Base Article: 169289 - Dynamic Host Configuration Protocol (DHCP) is a standard protocol defined by RFC 1541 (which is superseded by RFC 2131) that allows a server to dynamically distribute IP addressing and configuration information to clients.

DHCP FAQ
A great FAQ from Windows2000FAQ.com.

DHCP in Windows 2000
Overview of improvements and enhancements to Microsoft's DHCP service in Windows 2000. By Thomas Lee.

Options for Ipconfig.exe in Windows 2000
Microsoft Knowledge Base Article: 223413 - Ipconfig.exe is a command-line tool you can use to renew and release leases obtained from a Dynamic Host Configuration Protocol (DHCP - server, and display your IP settings. This article describes these and other Ipconfig features.

TCP/IP Address Management Using Windows NT DHCP Service
Microsoft Online Seminar: Understand core concepts, and learn how best to plan and install DHCP in your Windows NT© network.19 Minutes, 09/03/98.

Using DHCP to Manage the Assignment of IP Addresses
Microsoft Online Seminar: Learn to utilize DHCP to allow your network administration to automate and centrally manage the assignment of IP addresses in your organization's network. 17 Minutes, 09/03/98

General DHCP Articles

Changes in DHCP Client behavior in Windows 2000
Microsoft Knowledge Base Article: 255836 - A Windows 2000 client may lose connectivity to all network resources if it receives its IP configuration by using Dynamic Host Configuration Protocol (DHCP). Earlier-version clients that use DHCP may still have access to network resources.

Creating DHCP Scopes Using DHCP Manager
Microsoft Knowledge Base Article: 150565 - A DHCP scope is an administrative grouping of computers running the DHCP Client service. You create a scope for each subnet on the network to define parameters for that subnet.

Custom DHCP Client Identifiers for Windows NT
Microsoft Knowledge Base Article: 172408 - A Dynamic Host Configuration Protocol (DHCP) client will normally use the media access control address of its network interface card (NIC) to identify itself to a DHCP server. Windows NT DHCP clients can also have client identifiers manually configured.

DHCP Minimum Lease Duration
Microsoft Knowledge Base Article: 158016 - The Microsoft Windows NT DHCP Service has been designed to allow a network administrator to assign a lease duration shorter than one hour for testing purposes. Always assign a lease duration longer than one hour for production systems in real work environments.

DHCP Registers NetBIOS Names with DNS
Microsoft Knowledge Base Article: 222463 - If a Dynamic Host Configuration Protocol (DHCP) server is set to automatically register a Dynamic DNS (DDNS) server with client information, it passes the client information to the DNS server upon acknowledgment of the IP address reservation

DHCP: Spanning Multiple Subnets
Microsoft Knowledge Base Article: 120932 A DHCP (Dynamic Host Configuration Protocol) server can provide IP addresses to clients spanning multiple subnets if the router that separates them can act as an RFC 1542(BOOTP) relay agent.

How DHCP assigns network addresses to your computers Improving on DHCP
By Mark Minasi, Windows & .NET Magazine September 1996.

HOW TO: Add Novell SLP DHCP Options to the DHCP Service
This article describes how to add Novell Service Location Protocol (SLP) DHCP options to the DHCP service. You can configure the DHCP service that is included with Windows 2000 to provide DHCP options 78 and 79. Novell clients may require the.

HOW TO: Install and Configure a Windows 2000 DHCP Server in an Active Directory Domain
Microsoft Knowledge Base Article: 300429 - This step-by-step article describes how to build and configure a new Windows 2000 DHCP Server in a Windows 2000 Active Directory domain. The Windows 2000 DHCP service provides clients with IP addresses, and information such as the location of their default gateway, DNS servers, and WINS servers

HOW TO: Install and Configure a Windows 2000 DHCP Server in a Workgroup
Microsoft Knowledge Base Article: 301187 - This step-by-step guide describes how to configure a new Windows 2000-based Dynamic Host Configuration Protocol (DHCP) server on a standalone server to provide centralized management of IP addresses and other TCP/IP configuration settings for network clients.

Limitations Creating DHCP Reservations
Microsoft Knowledge Base Article: 196066 - DHCP manager will allow certain DHCP reservations outside the DHCP scope range but will deny if they are outside the subnet range. Several rules must apply when creating reservations.

Microsoft DHCP Vendor and User Classes
Microsoft Knowledge Base Article: 266675 - Describes vendor classes and user classes that are defined by default in Windows 2000 Dynamic Host Configuration Protocol (DHCP) server.

Understanding the DHCP Console Icons
Microsoft Knowledge Base Article: 259786 - Definitions of the icons used in the Dynamic Host Configuration Protocol (DHCP) snap-in in Microsoft Management Console are not included in online Help or ToolTips.

Understanding DHCP IP Address Assignment for RAS Clients
Microsoft Knowledge Base Article: 160699 - When Remote Access Service (RAS) uses Dynamic Host Configuration Protocol (DHCP) to obtain IP addresses for dial-in clients, only the IP address from the DHCP lease is passed to the RAS client. Other options in the DHCP scope are not.

Windows NT Does Not Provide Bootstrap Protocol (BOOTP) Service
Microsoft Knowledge Base Article: 124584 - Although Windows NT provides dynamic host configuration protocol (DHCP) services, and DHCP is based on the Bootstrap protocol (BOOTP), Windows NT does not provide BOOTP services.

How to Articles

How DHCP Assigns Network Addresses to Your Computers
By John Enck, Windows NT Magazine October 1995.

How to Add Novell SLP DHCP Options to the DHCP Service
Microsoft Knowledge Base Article: 285019 - This article describes how to add Novell Service Location Protocol (SLP) DHCP options to the DHCP service.

HOW TO: Appoint an Administrator for DHCP Server Services in Windows 2000
Microsoft Knowledge Base Article: 303540 - This step-by-step article describes how to add users to the Dynamic Host Configuration Protocol (DHCP) Administrators group.

How to Configure Dynamic Host Configuration Protocol Servers with Split Scopes
Microsoft Knowledge Base Article: 280473 - This article describes how to configure Dynamic Host Configuration Protocol (DHCP) servers with split scopes.

How to Disable NetBIOS Over TCP/IP By Using DHCP Server Options
Microsoft Knowledge Base Article: 313314 - The Windows 2000 DHCP server provides a Vendor Class option you can use to disable the NetBIOS over TCP/IP for DHCP client. This article describes how to do this.

HOW TO: Install and Configure a DHCP Server in a Workgroup in Windows 2000
Microsoft Knowledge Base Article: 301187 - This step-by-step guide describes how to configure a new Windows 2000-based Dynamic Host Configuration Protocol (DHCP) server on a standalone server to provide centralized management of IP addresses and other TCP/IP configuration settings for the client computers on a network.

How to Install Network Services Such as WINS and DNS in Windows 2000
Microsoft Knowledge Base Article: 261321 - The location for installing Windows Internet Name Service (WINS), Domain Name System (DNS), Dynamic Host Configuration Protocol (DHCP), and other network services has changed in Windows 2000.

How to Move a DHCP Database to Another Windows NT Server
Microsoft Knowledge Base Article: 130642 Windows NT provides an administration utility called Dynamic Host Configuration Protocol (DHCP) Manager (Dhcpadmn.exe) that allows you to manage DHCP servers. However, Dhcpadmn.exe does not allow you to move a database from a server to another.

How to Remove and Reinstall DHCP and Keep the DHCP Config
Microsoft Knowledge Base Article: 169229. It is sometimes necessary to remove and then reinstall the DHCP Server service. This article explains how to perform this procedure and maintain your DHCP server settings.

How to Restore a Corrupted DHCP Database File
Microsoft Knowledge Base Article: 173396 This article discusses methods that may be used to recover a corrupted Dynamic Host Configuration Protocol (DHCP) database.

How to Upgrade a WINS or DHCP Database to Windows 2000
Microsoft Knowledge Base Article: 215416 Describes how to upgrade a DHCP or WINS database from a Microsoft Windows NT 3.51 server to a Windows 2000 server.

How to Use DHCP to Provide RAS Clients with DHCP Options
Microsoft Knowledge Base Article: 232703 - You can now use the DHCP Relay agent with RAS to provide DHCP scope options to RAS clients. The RAS client continues to receive an IP address from the RAS server, but may use DHCPInform packets to obtain WINS addresses, DNS addresses, domain

How to Use Jetpack.exe to Compact a WINS or DHCP Database
Microsoft Knowledge Base Article: 145881 - Microsoft Windows NT Server includes a utility, Jetpack.exe, that can be used to compact a Windows Internet Name Service (WINS) or Dynamic Host Configuration Protocol (DHCP) database. Microsoft recommends that you compact the WINS database whenever it approaches 30 MB.

Increasing the Number of IP Addresses on a Subnet
Microsoft Knowledge Base Article: 255999 - This article describes methods you can use to change the number of IP hosts on any given subnet.

Installing DHCP and DDNS on a Domain Controller
Microsoft Knowledge Base Article: 255134 - Installing Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS) on the same computer may allow name "hijacking." Evaluate the information in this article to determine whether it applies to your environment. (updated 622000)

Known Bugs and Issues

Diagnose DHCP problems with ipconfig
The TCP/IP protocol may be complex, but it contains powerful troubleshooting tools. Source: EarthWeb (April 28, 2000)

Account Operators Can Configure DHCP on Domain Controllers
Microsoft Knowledge Base Article: 309625 - If DHCP is installed on a domain controller (DC -, the domain account operators group can modify the DHCP configuration, even though this ability should be limited to administrators and DHCP administrators.

DHCP Client May Fail to Obtain a DHCP-Assigned IP Address
Microsoft Knowledge Base Article: 167014 - When a DHCP client is moved from one subnet to another, it may fail to obtain a valid IP address on the new subnet.

DHCP Lease Grace Period Is Four Hours
Microsoft Knowledge Base Article: 261964 - After a Dynamic Host Configuration Protocol (DHCP) client lease expires, it is not immediately scavenged from the database. A grace period of four hours is added to the end of the lease to prevent against clock drift between the DHCP client and server. On a Windows 2000-based DHCP server, leases are scavenged from the database if they meet the criteria of (ExpirationTime + 4 hours).

DHCP May Register IP Address as Printer Name in DDNS
Microsoft Knowledge Base Article: 257600 - When you configure Windows 2000 Dynamic Host Configuration Protocol (DHCP) to update DNS zones for clients that do not support dynamic update, printers may be registered in forward-lookup zones and reverse-lookup zones using their DHCP-assigned

DHCP Renewal Failures on Switched Networks
Microsoft Knowledge Base Article: 168455 - A client connected to an Ethernet switch may not receive a renewed DHCP IP address during startup. Releasing and renewing the IP address manually works.

DHCP Server Attempts to Assign Reserved Addresses
Microsoft Knowledge Base Article: 284145 - Under certain conditions, on a scope with numerous exclusions and reservations, a Windows 2000 DHCP server may try to assign reserved addresses to non-reserved clients, and the following behavior may occur:

DHCP Server Does Not Issue IP Leases After You Run Dhcpexim.exe
Microsoft Knowledge Base Article: 287031 - After you use Dhcpexim.exe to move the DHCP scopes, the DHCP server does not issue internet protocol (IP) leases.

DHCP Server Does Not Update the A Record on the DNS Server If Option 81 Is Received with the S Bit Set
Microsoft Knowledge Base Article: 289583 - DHCP option 81 (option code 0x51, or decimal 81 - which is named FQDN (fully qualified domain name - allows a client to request that the DHCP server perform DNS name registration on behalf of the client.

DHCP Server May Offer a Zero-Length Lease Time If Conflict Detection Is Activated
Microsoft Knowledge Base Article: 269553 - When a client computer sends a discover request with a requested address that the Dynamic Host Configuration Protocol (DHCP) server cannot give to the client (the address may be excluded, reserved for another client, outside the scope range

DHCP Server May Not Release Address
Microsoft Knowledge Base Article: 285134 - When a client and server are on different subnets and the server does not have a scope defined for its local interface, the Windows 2000-based Dynamic Host Configuration Protocol (DHCP) server may not release an Internet Protocol (IP) address when the client sends a DHCP release message.

DHCP Server Handles the Global User Class Lease Option Incorrectly
Microsoft Knowledge Base Article: 298844 - If you set option 51 for the Lease time setting on the server by using the advanced options for Routing and Remote Access Service (RRAS) class clients, the server continues to hand out the default lease time to the class RRAS clients.

Duplicate Address Errors When Using Synoptics Hubs and DHCP
Microsoft Knowledge Base Article: 136568 - You may experience duplicate name errors and have problems obtaining IP addresses from Dynamic Host Configuration Protocol (DHCP) servers if you have Synoptics hubs on the network.

Event ID: 1008 After Upgrading Windows NT 4.0 DHCP or WINS Server to Windows 2000
Microsoft Knowledge Base Article: 247135 - After you upgrade from a Microsoft Windows NT 4.0 DHCP server or WINS server to use Windows 2000, an event is logged informing the administrator that the database needs to be upgraded if the jet database conversations fails.

Incorrect Subnet Mask and Options Assigned from Windows NT 4.0 DHCP Server
Microsoft Knowledge Base Article: 261489 - When you use a Windows 2000-based computer to obtain an Internet Protocol (IP) address from a Microsoft Windows NT 4.0 Dynamic Host Configuration Protocol (DHCP) server, you may receive a valid IP address but the options are not received

Jetpack Error Codes for Windows 2000 and Windows NT 4.0
Microsoft Knowledge Base Article: 172570 - This article lists the error codes and messages used by Jetpack.exe (the Microsoft Windows NT Server utility that can be used to compact a WINS or DHCP database) for Windows NT Server version 4.0.

Maximum of 854 DHCP Servers in Active Directory
Microsoft Knowledge Base Article: 264631 - You can define a maximum of 854 DHCP servers in Active Directory. If you try to authorize additional DHCP servers, you receive an error message

Multihomed DHCP Clients May Cause "Bad_Address" Entry on a DHCP Server in Windows 2000
A "bad_address" entry may be generated on a DHCP server. This problem may occur if: If the following commands are run on the DHCP client, one "bad_address" entry is generated on the DHCP server: ipconfig /release ipconfig /renew This address is the IP...

PXE Clients Do Not Receive IP Address From DHCP Server Across a Router
Microsoft Knowledge Base Article: 257579 - Pre-Boot Execution Environment (PXE) clients require an Internet Protocol (IP) address from a Dynamic Host Configuration Protocol (DHCP) server to begin the installation process from a Remote Installation Services (RIS) server.

The Default DHCP Gateway Is Not Added to the Routing Table on a Multihomed Computer
Microsoft Knowledge Base Article: 269879 - A default gateway that is received from a Dynamic Host Configuration Protocol (DHCP) server may not be added to the host's routing table and is therefore not used.

The Windows 2000 SP3 DHCP Tool May Show an Empty Reservations List
Microsoft Knowledge Base Article: 328636 - The Dynamic Host Configuration Protocol (DHCP) snap-in in Microsoft Management Console (MMC) may not show any reservations in a scope. This may occur after you install Windows 2000 Service Pack 3 (SP3) on an administrative workstation if there are more than 100 reservations in a scope.

Unable to Contact DHCP Server with RIS Boot Disk
Microsoft Knowledge Base Article: 255952 - When you start a Remote Install Service (RIS) client by using the Remote Install boot disk you created with the Remote Boot Floppy Generator (Rbfg.exe), you may receive an error message:

Using Dynamic Host Configuration Protocol Options 60, 66, 67 to Direct PXE Clients to RIS Servers May Fail
Microsoft Knowledge Base Article: 259670 - In some environments, you may try to set the following Dynamic Host Configuration Protocol (DHCP) options in order to direct Pre-Boot Execution Environment (PXE) clients to Windows 2000 Remote Installation Services (RIS) servers:

Windows 2000 DHCP Server Continues to Assign Addresses After Upgrade
Microsoft Knowledge Base Article: 225148 - After you upgrade a Microsoft Windows NT 4.0 server to Windows 2000, Dynamic Host Configuration Protocol (DHCP) continues to assign addresses, even though it is not authorized to do so.

Windows 2000 DHCP Server Gives Incorrect Settings for the Default Gateway or the DNS Server
Microsoft Knowledge Base Article: 263217 - In Microsoft Windows 2000 Server, Windows 2000 Advanced Server, and Windows 2000 Professional, you may experience the following behavior:

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