DHCP Server Performance Degraded by Large Number of Scopes

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This article was previously published under Q182047

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SYMPTOMS

When a large number of scopes are configured on a Windows NT 4.0 DHCP server, performance degrades to where it cannot keep up with large client loads such as those experienced after a power failure, or at peak network startup times.

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CAUSE

A list of scopes is maintained in the registry. When a DHCP DISCOVER or DHCP REQUEST is received, it must be matched against the configured scopes to see if the server is able to provide services to the client subnet. This process of searching through the scopes was not optimized for large numbers of scopes. Additionally, some database calls could experience suboptimal performance caused by nonoptimal database buffer initialization.

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RESOLUTION

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

152734 (http://support.microsoft.com/kb/152734/EN-US/ ) How to Obtain the Latest Windows NT 4.0 Service Pack

NOTE: This hotfix supersedes the fixes referred to in the following articles in the Microsoft Knowledge Base:

ARTICLE-ID: 141496 (http://support.microsoft.com/kb/141496/EN-US/ )
TITLE : DHCP Client Comment Disappears When Obtaining IP Address

ARTICLE-ID: 167708 (http://support.microsoft.com/kb/167708/EN-US/ )
TITLE : BootP Client Names Disappear in DHCP Manager

ARTICLE-ID: 163055 (http://support.microsoft.com/kb/163055/EN-US/ )
TITLE : DHCP Client May Fail with WinNT 4.0 SP2 Multinetted DHCP Server

ARTICLE-ID: 175035 (http://support.microsoft.com/kb/175035/EN-US/ )
TITLE : Diskless Workstations Cannot Find BOOTP Server with DHCP

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STATUS

Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.

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MORE INFORMATION

The updated file caches the entire scope list in memory, and uses a binary search to quickly determine if the server has a scope that is relevant to each client request. This update dramatically reduces the number of times that registry keys are opened and searched. It also provides more buffers for interaction with the database, which improves database throughput.

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