如果你正在尝试和学习ping网站，你可能会惊讶于基于“什么”你平的结果。今天的超级用户问答文章帮助一个困惑和沮丧的读者澄清问题。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

截图由Cristianzambrano（Wikimedia Comm***）提供。

问题

超级用户读者Saransh Singh想知道使用和不使用http://ping的区别是：

I am trying to ping my website http://www.example.com/ and it resolves to an unknown IP address, then it times out.

But when I ping example.com, it works. What am I missing or not understanding here?

Note: example.com was substituted for the actual website at SuperUser.

使用和不使用http://ping有什么区别？

答案

超级用户贡献者DavidPostill为我们提供了答案：

The argument to ping is a host name (or an IP address). So the following will all work:

On the other hand, this will not work as http://www.example.com/ is an HTTP Uniform Resource Locator (URL), not a valid host name (although part of it is a host name).

A HTTP URL is made up of 4 parts:

• Scheme — Always present
• Host Name — Always present
• Path or Stem — Always present but sometimes is null
• Parameters — Optional

A ping will not normally recognize URLs as a valid destination host name.

Note

Not all URLs have the format mentioned above. A complete URL c***ists of a naming scheme specifier followed by a string whose format is a function of the naming scheme. The format of URLs is defined in the IETF specification Uniform Resource Locators (URLs). *This is a different website address from the one shown for URL above.

DNS Hijacking

An exception to the above can happen if the DNS server (which resolves host names to IP addresses) is configured to return a valid IP address even if an invalid host name is supplied. This can happen if an ISP is hijacking your DNS queries.

From the answer Why is ping resolving to an IP 198.105.254.228 for any random host name that i type? by Michael Hampton:

• They are trying to be “helpful” by redirecting requests for nonexistent domains to a white label service that provides search results and advertising, from which everyone but you gets a cut of the revenue. Fortunately, they do have a preferences page where you can supposedly turn it off.

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