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DNS客户端上配置了DNS服务器的地址。通常,这些服务器是一个域的成员并经认证。 所有域名解析请求全从一条到到其中一台本地服务器的请求开始。DNS查询可以有两种形式:

• 一个 递归 查询要求域名服务器完全解析一个域名, 并返回结果。如果不能直接回复该请求, 这个域名服务器查询自己的配置和缓存，找一个上一级服务器以获取更多的信息。 最糟糕的情况时, 这可能是一个根域的预配置服务器清单。 这些地址被返回的动作被称为一次 送交. 本地的域名服务器必须马上将其请求发送到这些服务器之一。
• 通常, 这将是一次 iterative query, which asks the second nameserver to either respond with an authoritative reply, or with the addresses of nameservers (NS records) listed in its tables or caches as authoritative for the relevant zone. The local nameserver then makes iterative queries, walking the tree downwards until an authoritative answer is found (either positive or negative) and returned to the client.

In some configurations, such as when firewalls prevent direct IP communications between DNS clients and external nameservers, or when a site is connected to the rest of the world via a slow link, a nameserver can be configured with information about a forwarder. This is an external nameserver to which the local nameserver should make requests as a client would, asking the external nameserver to perform the full recursive name lookup, and return the result in a single query (which can then be cached), rather than reply with referrals.