DNS 查询中域名重复

Question

你描述的行为几乎是正常的、已知的和有记录的行为。

发生的情况是，当解析器无法解析 DNS 名称时，它将尝试解析它，并将search指令中的所有域依次附加到原始查询中（如果在中间过程中没有匹配）。

该过程本身有点复杂，并且由于该过程的递归性质，可以组合多个搜索域。

在解析 DNS 名称时，在某种程度上最小化/避免域扩展的方法是在指令中search（或在您配置搜索域的任何位置），甚至在应用程序级别，以“.”结尾 DNS/域名。

如：

search domainspec.com. domain.com. example.com.

另外，举个例子，在进行 ping 时，也可以根据具体情况避免域搜索扩展：

ping www.example.com.

或者

ping www.cnn.com.

从人 resolv.conf(5)

search 主机名查找的搜索列表。

          The search list is normally determined from the local domain
          name; by default, it contains only the local domain name.
          This may be changed by listing the desired domain search path
          following the search keyword with spaces or tabs separating
          the names.  Resolver queries having fewer than ndots dots
          (default is 1) in them will be attempted using each component
          of the search path in turn until a match is found.  For
          environments with multiple subdomains please read options
          ndots:n below to avoid man-in-the-middle attacks and
          unnecessary traffic for the root-dns-servers.  Note that this
          process may be slow and will generate a lot of network traffic
          if the servers for the listed domains are not local, and that
          queries will time out if no server is available for one of the
          domains.

          The search list is currently limited to six domains with a
          total of 256 characters.

Answer 1