Disable DNS client screening in Windows Server 2003

Windows Server 2003 has a new DNS feature called client screening, which allows the server to determine and remember if a given DNS server is accessible. If the server can't reach a given DNS server, it's marked as unreachable in its lookup cache and will not be used for further lookups until either the system is restarted or the cache expires or is manually cleared.

There are pros and cons to this approach. On the plus side, since a DNS server that's marked as unreachable won't be used in future DNS lookups, future lookups may take less time. On the downside, this can create problems for servers that are multi-homed (i.e., have more than one network adapter). A DNS server that's not reachable from one interface may be reachable from another -- and might be wrongly marked as unreachable.

Normally this should not create a problem. But if it does -- for instance, if you have a computer with multiple interfaces connected to the Internet -- there is a way you can disable it. Here's what to do:

Open the Registry on the affected computer and navigate to the value HKEY_LOCAL

To read more you must become a member of SearchWindowsServer.com

As an existing member of the TechTarget network please provide your password to activate your account (Forgot your password?):

Password:

By joining SearchWindowsServer.com you agree to receive email updates from the TechTarget network of sites, including updates on new content, magazine or event notifications, new site launches and market research surveys. Please verify all information and selections above. You may unsubscribe at any time from one or more of the services you have selected by editing your profile or unsubscribing via email.

TechTarget cares about your privacy. Read our Privacy Policy

Digg This!     StumbleUpon     Del.icio.us

RELATED CONTENT Windows Server Monitoring and Management DirectAccess means 'always on' in Windows Server 2008 R2 Simple tools and techniques for finding Windows memory leaks Top Windows server hardening standards and guidelines Hyper-V gains new resiliency features with Windows Server 2008 R2 Troubleshooting Windows print spooler crashes Windows server hardening: How much is enough? Terminal Services grows up with Windows Server 2008 R2 Top five Server Core management tips for Windows 2008 Windows Server 2008 R2: Not your father's R2 upgrade The bottom line on Microsoft Hyper-V Microsoft Windows Server 2003 Administration How to install Windows Server 2003 patches when offline Validating Windows server clusters with ClusPrep Exploring the Windows Server 2003 Resource Kit: Clusfileport.dll Exploring the Windows Server 2003 Resource Kit: Cmdhere.inf and CMGetCer.inf Windows server security management: Security expert roundup Windows server management with Remote Desktop Avoid DC restoration problems with authoritative restore Exploring the Windows Server 2003 Resource Kit: Confdisk.exe Exploring the Windows Server 2003 Resource Kit: Compress.exe and Expand.exe Exploring the Windows Server 2003 Resource Kit: Clusterrecovery.exe Microsoft Windows Server 2003 Administration Research

RELATED RESOURCES 2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems Search Bitpipe.com for the latest white papers and business webcasts Whatis.com, the online computer dictionary

_MACHINE\SYSTEM\CurrentControlSet\Services\
Dnscache\Parameters.

Add a new DWORD value named ScreenUnreachableServers and set it to 0, and then stop and restart the DNS Client Service.

Note: You should not use this feature unless you are experiencing serious problems, such as lookup failures, and can't work around the problem any other way (for instance, by changing the IP address of the DNS server).

Why does this happen on a system-wide versus a per-adapter basis? My guess is that there's no way for the system to really know about changes to the topology of the network outside. If a DNS server goes unreachable for one adapter, there's no guarantee that it will not be unreachable for another as well, and so it's excluded.

About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter. Check it out for the latest advice and musings on the world of Windows network administrators. He is also the author of the book Windows Server Undocumented Solutions.

More information from SearchWinSystems.com

Rate this Tip To rate tips, you must be a member of SearchWindowsServer.com. Register now to start rating these tips. Log in if you are already a member. Submit a Tip DISCLAIMER: Our Tips Exchange is a forum for you to share technical advice and expertise with your peers and to learn from other enterprise IT professionals. TechTarget provides the infrastructure to facilitate this sharing of information. However, we cannot guarantee the accuracy or validity of the material submitted. You agree that your use of the Ask The Expert services and your reliance on any questions, answers, information or other materials received through this Web site is at your own risk.