了解DNS服务器的转发功能 (dns服务器 转发)
Title: Understanding the Forwarding Function of DNS Servers
Introduction
Domn Name System (DNS) is an essential component of the internet that translates human-readable domn names into IP addresses that computers can understand. DNS servers store and manage domn name records and respond to client requests for name resolution. DNS servers use various mechanis, including caching and forwarding, to speed up name resolution and reduce network traffic. This article focuses on DNS server forwarding, exploring its definition, purpose, and configurations.
What is DNS Server Forwarding?
DNS forwarding is a mechani that allows a DNS server to redirect client requests for name resolution to other DNS servers. For instance, when a DNS server receives a request for a domn name that is not within its authority, it can forward the request to another DNS server that has the required information. The forwarding DNS server acts as an intermediary between the client and the authoritative DNS server.
DNS server forwarding is particularly useful in networks that have multiple DNS servers with different areas of authority. For example, an organization may have a local DNS server that manages internal domn names and forwards external requests to public DNS servers. DNS forwarding can reduce the load on authoritative DNS servers, improve name resolution speed, and provide redundancy and fault tolerance.
DNS Server Forwarding Configuration Options
There are three common ways to configure DNS server forwarding:
1. Conditional Forwarding
Conditional forwarding is a configuration where a DNS server forwards requests for specific domn names to specific DNS servers. This configuration works by creating a list of domn names and their corresponding authoritative DNS servers, which the forwarding DNS server uses to direct requests. Conditional forwarding is useful in situations where network administrators want to optimize name resolution for specific domns or reduce network traffic.
2. Forwarders
Forwarders are a global setting in a DNS server that specifies a list of DNS servers that the server will forward all requests to that it cannot resolve itself. The forwarding DNS server sends all requests to the specified DNS servers, which act as the intermediary between the client and the authoritative DNS servers. Forwarders are useful in situations where DNS servers have a limited view of the internet and require external DNS servers to handle requests for external domns.
3. DNS Delegation
DNS delegation is a configuration option where a DNS server delegates specific subdomns to other DNS servers. DNS delegation occurs when a domn owner wants to have some control over a subdomn, but the DNS server that manages the parent domn is not the appropriate authority. In this configuration, the managing DNS server sets up a DNS delegation record that refers to the appropriate DNS server as the authority for the subdomn.
Conclusion
In summary, DNS server forwarding is a vital mechani that enables DNS servers to redirect client requests for name resolution to other DNS servers. DNS forwarding provides several benefits, including reducing the load on authoritative DNS servers, improving name resolution speed, and providing redundancy and fault tolerance. Network administrators can configure DNS forwarding in several ways, including conditional forwarding, forwarders, and DNS delegation, depending on their specific requirements. Understanding these configurations can help organizations optimize their DNS infrastructure and reduce network traffic.
相关问题拓展阅读：
DNS 中的转发查询是怎么理解?
1.使用DNS转发器
DNS转发器是为其他DNS服务器完成DNS查询的DNS服务器。使用DNS转发器的主要目的是减轻DNS处理的压力,把查询请求从DNS服务器转给转发器, 从DNS转发器潜在地更大DNS高速缓存中受益。
使用DNS转发器的另一个好处是它阻止了DNS服务器转发来自互联网DNS服务器的查询请求。如果你的DNS服务器保存了你内部的域DNS资源记录的话, 这一点就非常重要。不让内部DNS服务器进行递归查询并直接联系DNS服务器,而是让它使用转发器来处理未授权的请求。
2.使用只缓冲DNS服务器
只缓冲DNS服务器是针对为授权域名的。它被用做递归查询或者使用转发器。当只缓冲DNS服务器收到一个反馈,它把结果保存在高速缓存中,然后把 结果发送给向它提出DNS查询请求的系统。随着时间推移伍森,只缓冲DNS服务器可以收集大量的DNS反馈,这能极大地缩短它提供DNS响应的时间。
把只缓冲DNS服务器作为转发器使用,在你的管理控制下,可以提高组织安全性。内部DNS服务器可以把只缓冲DNS服务器当作自己的转发器,只缓冲 DNS服务器代替你的内部DNS服务器完成递归查询。使用你自己的只缓冲DNS服务器作为转发器能够提高安全性,因为你不需要依赖你的ISP的DNS服务 器作为转发器,在你不能确认ISP的DNS服务器安全性的情况下,更是如此。
3.使用DNS广告者(DNS advertisers)
DNS广告者是一台负责解析域中查询的DNS服务器。例如,如果你的主机对于domain.com 和corp.com是公开可用的资源,你的公共DNS服务器就应该为 domain.com 和corp.com配置DNS区文件。
除DNS区文件宿主的其他DNS服务器之外的DNS广告者设置,是DNS广告者只回答其授权的域名的查询。这种DNS服务器不会对其他DNS服务器进行递归 查询。这让用户不能使用你的公共DNS服务器来解析其他域名。通过减少与运行一个公开DNS解析者相关的风险,包括缓存中毒,增加了安全。
4.使用DNS解析者
DNS解析者是一台可以完成递归查询的DNS服务器,它能够解析为授权的域名。例如,你可能在内部网络上有一台DNS服务器,授权内部网络域名 internalcorp.com的DNS服务器。当网络中的客户机使用这台DNS服务器去解析techrepublic.com时,这台DNS服务器通过向其他DNS服务器查询来执行递归 以获得答案。
DNS服务器和DNS解析者之间的区别是DNS解析者是仅仅针对解析互联网主机名。DNS解析者可以是未授权DNS域名的只缓存DNS服务器。你可以让DNS 解析者仅对内部用户使用,你也可以让它仅为外部用户服务,这样你就不用在没有办法控制的外部设立DNS服务器了,从而提高了安全性。当然,你也 可以让DNS解析者同时被内、外部用户使用。
5.保护DNS不受缓存污染
DNS缓存污染已经成了日益普遍的问题。绝大部分DNS服务器都能够将DNS查询结果在旁念答复给发出请求的主机之前,就保存在高速缓存中。DNS高速缓存 能够极腔启亩大地提高你组织内部的DNS查询性能。问题是如果你的DNS服务器的高速缓存中被大量假的DNS信息“污染”了的话,用户就有可能被送到恶意站点 而不是他们原先想要访问的网站。
绝大部分DNS服务器都能够通过配置阻止缓存污染。Windows Server 2023 DNS服务器默认的配置状态就能够防止缓存污染。如果你使用的是Windows 2023 DNS服务器,你可以配置它,打开DNS服务器的Properties对话框,然后点击“高级”表。选择“防止缓存污染”选项,然后重新启动DNS服务器。
DNS查询分两种
1 递归查询 用户输入查询后服务器返回的是最终的查睁没乱询结果或者解答
2 迭代查询 查询的不是该域名的授权服务器，就返回悉档一个他认察旅为可以解析这个查询的服务器的IP地址，因此用户要向多个服务器进行查询
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