[譯]管理Windows 2000 Pro中的DNS用戶端緩衝

http://techrepublic.com.com/5100-10877_11-6029680.html?tag=nl.e116

Manage the DNS client cache in Windows 2000 Pro
管理Windows 2000 Pro中的DNS用戶端緩衝

by  Jim Boyce
作者：purple endurer
Keywords:  Windows 2000 | Microsoft Windows | Domain names
關鍵字：Windows 2000 | Microsoft Windows | 網域名稱

 

Takeaway:
If a lookup fails for a host because the target domain's DNS server is down, then subsequent attempts to look up the host will also fail because the failed results are cached. Learn two ways to overcome this problem.
概述：
如果對一個主機的查詢因為負責其網域名稱解析的DNS伺服器關閉而失敗，那麼後續的查詢該主機的嘗試也將因為（先前的）失敗結果被緩衝而不成功。讓我們學習克服這個問題的兩種方法。

 

DNS enables fully qualified host names like www.techrepublic.com to be resolved to their target IP addresses. Every time you visit a Web site, the DNS client software built into Windows 2000 Professional performs a DNS lookup of the specified host name to obtain the IP address of the target server.
DNS能使www.techrepublic.com這樣的完全合法的主機名稱被解析為目標IP地址。您每次訪問一個網站，Windows 2000 Professional內建的DNS用戶端軟體執行一次指特主機名稱的查詢以獲得目標伺服器的IP地址。

The DNS client caches the results of each name lookup to speed up subsequent requests for the address. The default cache timeout is 30 minutes. If a lookup result is longer than 30 minutes, Windows performs an external lookup of the host and refreshes the cached copy.
DNS用戶端緩衝查詢的每一個名字，用以加速後續的地址請求。預設緩衝時限為30分鐘。如果一個查詢結果長於30分鐘，Windows執行一個主機擴充查詢並重新整理緩衝拷貝。

Although caching can improve name resolution performance, it can also affect resolution in a negative way. In addition to caching positive results, Windows also caches negative results. So, if a lookup fails for a host because the target domain's DNS server is down, then subsequent attempts to look up the host will also fail because the failed results are cached. You can overcome this problem in one of two ways: flush the DNS cache and try again when the server comes back on line, or change the cache timeout.
儘管緩衝能改善名字解析效能，但它也能負面影響解析。除了緩衝有效結果之外，Windows也緩衝不良結果。所以，如果對一個主機的查詢因為負責其網域名稱解析的DNS伺服器關閉而失敗，那麼後續的查詢該主機的嘗試也將因為（先前的）失敗結果被緩衝而不成功。您可以用下列兩種方法之一克服這個問題：重新整理DNS緩衝並在伺服器重新上線時重試，或者修改緩衝時限。

To change cache timeout, open the Registry Editor and add the DWORD value
要修改緩衝時限，開啟登錄編輯程式並增加DWORD型值：

HKEY_CURRENT_USER/Software/Microsoft/Windows/CurrentVersion/Internet Settings/DnsCacheTimeout.

Set the value of DnsCacheTimeout to the number of seconds you want entries to be cached.
按你所想，以秒為單位設定DnsCacheTimeout值。

To flush the DNS cache altogether, use the following command at a console prompt:
要重新整理DNS緩衝，在命令控制台使用下列命令：

ipconfig /flushdns

Note: Editing the registry is risky, so be sure you have a verified backup before saving any changes.