DNS Question

15 pts.
Tags:
DNS
DNS queries
It is my understanding that DNS simply maps a domain name into an IP address.  I realize that there is a lot more involved behind the scenes and there is other functionality, and perhaps some of that will explain what I am seeing. If I enter the address http://volokh.com/ into a web browser, it displays a web page for "The Volokh Conspiracy".  If I use ping, nslookup, or tracert with the domain name "volokh.com", they all tell me that it maps to IP address 174.37.144.148.  But when I enter http://174.37.144.148/ into my web browser, I get a different web page - a "placeholder page" for some software called "cPanel" running under Apache. Any idea what is going on?  Shouldn't this give me "The Volokh Conspiracy"? Thanks in advance for your replies.

Software/Hardware used:
Windows XP, Firefox
ASKED: February 1, 2010  7:15 AM
UPDATED: February 1, 2010  5:49 PM

Answer Wiki

Thanks. We'll let you know when a new response is added.

There are probably many different websites running off of the 174.37.144.148 IP address. It is quite common to have all the websites which are hosted by the same physical server use the same IP address. Because of this if you browse directly to the IP address the web server doesn’t know which web page to display so it displays the default website which is setup on the server which is usually the placeholder page.

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What you describe is a standard method of hosting multiple websites on one IP address. The technical term is “host header names”. So, when the webserver receives http traffic to a specific IP address, the traffic wil be directed to the appropriate website using the http host header name. See this <a href=”http://www.lmgtfy.com/?q=host+header”>Google search for more details on host header names</a>.

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  • JPMcGrath
    Thanks for your answers; they have been most helpful. Just to confirm that I grok this: The client system uses DNS to translate "volokh.com" to "174.37.144.148" and sends the HTTP request to that address. While at the TCP/IP level, the packet is not addressed to "volokh.com", the web client includes an HTTP HOST header that specifies "volokh.com". When the web server (Apache in this case) receives the HTTP request, it looks at the HOST header and decides which content to serve based on that. So when I browse to http://174.37.144.148/, it gets to the same web server, but it does not know that I am looking for the "volokh.com" content and serves content based on the defaults. Is this correct?
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  • Labnuke99
    You have summarized the process exactly.
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