<title>Issues Regarding DNS and Apache HTTP Server - Apache HTTP Server</title>
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-<p class="apache">Apache HTTP Server Version 2.3</p>
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+<p class="apache">Apache HTTP Server Version 2.5</p>
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-<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="./">Version 2.3</a></div><div id="page-content"><div id="preamble"><h1>Issues Regarding DNS and Apache HTTP Server</h1>
+<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="./">Version 2.5</a></div><div id="page-content"><div id="preamble"><h1>Issues Regarding DNS and Apache HTTP Server</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="./en/dns-caveats.html" title="English"> en </a> |
<a href="./fr/dns-caveats.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
<li><img alt="" src="./images/down.gif" /> <a href="#denial">Denial of Service</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#main">The "main server" Address</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#tips">Tips to Avoid These Problems</a></li>
-</ul></div>
+</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="example" id="example">A Simple Example</a></h2>
- <div class="example"><p><code>
- # This is a misconfiguration example, do not use on your server <br />
- <VirtualHost www.example.dom> <br />
- ServerAdmin webgirl@example.dom <br />
- DocumentRoot /www/example <br />
- </VirtualHost>
- </code></p></div>
+ <pre class="prettyprint lang-config">
+# This is a misconfiguration example, do not use on your server
+<VirtualHost www.example.dom>
+ ServerAdmin webgirl@example.dom
+ DocumentRoot /www/example
+</VirtualHost>
+ </pre>
+
<p>In order for the server to function properly, it absolutely needs
to have two pieces of information about each virtual host: the
<p>Suppose that <code>www.example.dom</code> has address 192.0.2.1.
Then consider this configuration snippet:</p>
- <div class="example"><p><code>
- # This is a misconfiguration example, do not use on your server <br />
- <VirtualHost 192.0.2.1> <br />
- ServerAdmin webgirl@example.dom <br />
- DocumentRoot /www/example <br />
- </VirtualHost>
- </code></p></div>
+ <pre class="prettyprint lang-config">
+# This is a misconfiguration example, do not use on your server
+<VirtualHost 192.0.2.1>
+ ServerAdmin webgirl@example.dom
+ DocumentRoot /www/example
+</VirtualHost>
+ </pre>
+
<p>This time httpd needs to use reverse DNS to find the
<code>ServerName</code> for this virtualhost. If that reverse
<p>Here is a snippet that avoids both of these problems:</p>
- <div class="example"><p><code>
- <VirtualHost 192.0.2.1> <br />
- ServerName www.example.dom <br />
- ServerAdmin webgirl@example.dom <br />
- DocumentRoot /www/example <br />
- </VirtualHost>
- </code></p></div>
+ <pre class="prettyprint lang-config">
+<VirtualHost 192.0.2.1>
+ ServerName www.example.dom
+ ServerAdmin webgirl@example.dom
+ DocumentRoot /www/example
+</VirtualHost>
+ </pre>
+
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="denial" id="denial">Denial of Service</a></h2>
<p>Consider this configuration snippet:</p>
- <div class="example"><p><code>
- <VirtualHost www.example1.dom><br />
- <span class="indent">
- ServerAdmin webgirl@example1.dom<br />
- DocumentRoot /www/example1<br />
- </span>
- </VirtualHost><br />
- <br />
- <VirtualHost www.example2.dom><br />
- <span class="indent">
- ServerAdmin webguy@example2.dom<br />
- DocumentRoot /www/example2<br />
- </span>
- </VirtualHost>
- </code></p></div>
+ <pre class="prettyprint lang-config">
+<VirtualHost www.example1.dom>
+ ServerAdmin webgirl@example1.dom
+ DocumentRoot /www/example1
+</VirtualHost>
+<VirtualHost www.example2.dom>
+ ServerAdmin webguy@example2.dom
+ DocumentRoot /www/example2
+</VirtualHost>
+ </pre>
+
<p>Suppose that you've assigned 192.0.2.1 to
<code>www.example1.dom</code> and 192.0.2.2 to
users typed in URLs of the form
<code>http://www.example2.dom/whatever</code>) will all be served by
the <code>example1.dom</code> virtual host. To better understand why
- this happens requires a more in-depth discussion of how httpd
+ this happens requires a more in-depth discussion of how httpd
matches up incoming requests with the virtual host that will
serve it. A rough document describing this <a href="vhosts/details.html">is available</a>.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
or maybe <code>/etc/nsswitch.conf</code>.</p>
<p>If your server doesn't have to perform DNS for any other
- reason then you might be able to get away with running httpd
+ reason then you might be able to get away with running httpd
with the <code>HOSTRESORDER</code> environment variable set to
"local". This all depends on what OS and resolver libraries you
are using. It also affects CGIs unless you use
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+</div><div class="top"><a href="#page-header"><img src="./images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
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