如果你正在嘗試和學習ping網站，你可能會驚訝於基於“什麼”你平的結果。今天的超級使用者問答文章幫助一個困惑和沮喪的讀者澄清問題。

今天的問答環節是由SuperUser提供的，SuperUser是Stack Exchange的一個分支，是一個由社群驅動的問答網站分組。

截圖由Cristianzambrano（Wikimedia Comm***）提供。

問題

超級使用者讀者Saransh Singh想知道使用和不使用http://ping的區別是：

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有什麼區別？

答案

超級使用者貢獻者DavidPostill為我們提供了答案：

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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