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<?xml version="1.0" encoding="ISO-8859-1"?>
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<title>Name-based Virtual Host Support - Apache HTTP Server</title>
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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> > <a href="./">Virtual Hosts</a></div><div id="page-content"><div id="preamble"><h1>Name-based Virtual Host Support</h1>
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<p>This document describes when and how to use name-based virtual hosts.</p>
</div>
<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#namevip">Name-based vs. IP-based Virtual Hosts</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#alg">How the server selects the proper name-based virtual host</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#using">Using Name-based Virtual Hosts</a></li>
</ul><h3>See also</h3><ul class="seealso"><li><a href="ip-based.html">IP-based Virtual Host Support</a></li><li><a href="details.html">An In-Depth Discussion of Virtual Host Matching</a></li><li><a href="mass.html">Dynamically configured mass virtual hosting</a></li><li><a href="examples.html">Virtual Host examples for common setups</a></li></ul></div>
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<div class="section">
<h2><a name="namevip" id="namevip">Name-based vs. IP-based Virtual Hosts</a></h2>
<p><a href="ip-based.html">IP-based virtual hosts</a> use the IP address of the connection to
determine the correct virtual host to serve. Therefore you need to
have a separate IP address for each host.</p>
<p>With name-based virtual hosting, the server relies on the client to
report the hostname as part of the HTTP headers. Using this technique,
many different hosts can share the same IP address.</p>
<p>Name-based virtual hosting is usually simpler, since you need
only configure your DNS server to map each hostname to the correct
IP address and then configure the Apache HTTP Server to recognize
the different hostnames. Name-based virtual hosting also eases
the demand for scarce IP addresses. Therefore you should use
name-based virtual hosting unless there is a specific reason to
choose IP-based virtual hosting. Some reasons why you might consider
using IP-based virtual hosting:</p>
<ul>
<li>Name-based virtual hosting often <a href="../ssl/ssl_faq.html#vhosts">
cannot be used with SSL secure servers</a>
because of the nature of the SSL protocol.</li>
<li>Some operating systems and network equipment implement bandwidth
management techniques that cannot differentiate between hosts unless
they are on separate IP addresses.</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="alg" id="alg">How the server selects the proper name-based virtual host</a></h2>
<p>It is important to recognize that the first step in name-based virtual
host resolution is IP-based resolution. Name-based virtual host
resolution only chooses the most appropriate name-based virtual host
after narrowing down the candidates to the best IP-based match. Using a wildcard (*)
for the IP address in all of the NameVirtualHost and VirtualHost directives makes this
IP-based mapping irrelevant.</p>
<p>When a request arrives, the server will first check if it is using
an IP address that matches exactly any <code class="directive"><a href="../mod/core.html#namevirtualhost">NameVirtualHost</a></code>. If it is, then it will look at each <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> section with a (literal) matching
IP address and try to find one where the <code class="directive"><a href="../mod/core.html#servername">ServerName</a></code> or <code class="directive"><a href="../mod/core.html#serveralias">ServerAlias</a></code>
matches the requested hostname. If it finds one, then it uses the configuration
for that server.</p>
<p><a name="defaultvhost" /> If no matching ServerName or ServerAlias is found in the
set of virtual hosts matching the NameVirtualHost directive, then
<strong>the first listed virtual host</strong> that matches the IP
address will be used.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="using" id="using">Using Name-based Virtual Hosts</a></h2>
<table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="../mod/core.html">core</a></code></li></ul></td><td><ul><li><code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code></li><li><code class="directive"><a href="../mod/core.html#namevirtualhost">NameVirtualHost</a></code></li><li><code class="directive"><a href="../mod/core.html#serveralias">ServerAlias</a></code></li><li><code class="directive"><a href="../mod/core.html#servername">ServerName</a></code></li><li><code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code></li></ul></td></tr></table>
<p>To use name-based virtual hosting, you must designate the IP
address (and possibly port) on the server that will be accepting
requests that need to be distinguished by hostname.
This is configured using the <code class="directive"><a href="../mod/core.html#namevirtualhost">NameVirtualHost</a></code> directive.
In the normal case where any and all IP addresses on the server should
be used, you can use <code>*</code> as the argument to <code class="directive"><a href="../mod/core.html#namevirtualhost">NameVirtualHost</a></code>. If you're planning to use
multiple ports (e.g. running SSL) you should add a Port to the argument,
such as <code>*:80</code>.</p>
<div class="note"><p>Note that mentioning an IP address in a
<code class="directive"><a href="../mod/core.html#namevirtualhost">NameVirtualHost</a></code> directive does not
automatically make the server <em>listen</em> to that IP address. See
<a href="../bind.html">Setting which addresses and ports Apache uses</a>
for more details. In addition, any IP address specified here must be
associated with a network interface on the server.</p></div>
<p>The next step is to create a <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> block for
each different host that you would like to serve. The argument to the
<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> directive
must match a defined <code class="directive"><a href="../mod/core.html#namevirtualhost">NameVirtualHost</a></code> directive. (In this usual case,
this will be "*:80"). Inside each <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> block, you will need at minimum a
<code class="directive"><a href="../mod/core.html#servername">ServerName</a></code> directive to designate
which host is served and a <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>
directive to show where in the filesystem the content for that host
lives.</p>
<div class="note"><h3>Main host goes away</h3>
<p> Any request that doesn't match an existing <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> is handled by the global
server configuration, regardless of the hostname or ServerName.</p>
<p> When you add a name-based virtual host to an existing server, and
the virtual host arguments match preexisting IP and port combinations,
requests will now be handled by an explicit virtual host. In this case,
it's usually wise to create a <a href="#defaultvhost">default virtual host</a>
with a <code class="directive"><a href="../mod/core.html#servername">ServerName</a></code> matching that of
the base server. New domains on the same interface and port, but
requiring separate configurations, can then be added as subsequent (non-default)
virtual hosts.</p>
</div>
<p>For example, suppose that you are serving the domain
<code>www.example.com</code> and you wish to add the virtual host
<code>other.example.com</code>, which points at the same IP address.
Then you simply add the following to <code>httpd.conf</code>:</p>
<div class="example"><p><code>
NameVirtualHost *:80<br />
<br />
<VirtualHost *:80><br />
<span class="indent">
# This first-listed virtual host is also the default for *:80
ServerName www.example.com<br />
ServerAlias example.com *.example.com<br />
DocumentRoot /www/domain<br />
</span>
</VirtualHost><br />
<br />
<VirtualHost *:80><br />
<span class="indent">ServerName other.example.com<br />
DocumentRoot /www/otherdomain<br />
</span>
</VirtualHost><br />
</code></p></div>
<p>You can alternatively specify an explicit IP address in place of the
<code>*</code> in both the <code class="directive"><a href="../mod/core.html#namevirtualhost">NameVirtualHost</a></code> and <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> directives. For example, you might want to do this
in order to run some name-based virtual hosts on one IP address, and either
IP-based, or another set of name-based virtual hosts on another address.</p>
<p>Many servers want to be accessible by more than one name. This is
possible with the <code class="directive"><a href="../mod/core.html#serveralias">ServerAlias</a></code>
directive, placed inside the <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> section. For example in the first <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> block above, the
<code class="directive"><a href="../mod/core.html#serveralias">ServerAlias</a></code> directive indicates that
the listed names are other names which people can use to see that same
web site:</p>
<div class="example"><p><code>
ServerAlias example.com *.example.com
</code></p></div>
<p>then requests for all hosts in the <code>example.com</code> domain will
be served by the <code>www.example.com</code> virtual host. The wildcard
characters <code>*</code> and <code>?</code> can be used to match names.
Of course, you can't just make up names and place them in <code class="directive"><a href="../mod/core.html#servername">ServerName</a></code> or <code>ServerAlias</code>. You must
first have your DNS server properly configured to map those names to an IP
address associated with your server.</p>
<p>Finally, you can fine-tune the configuration of the virtual hosts
by placing other directives inside the <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> containers. Most directives can be
placed in these containers and will then change the configuration only of
the relevant virtual host. To find out if a particular directive is allowed,
check the <a href="../mod/directive-dict.html#Context">Context</a> of the
directive. Configuration directives set in the <em>main server context</em>
(outside any <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>
container) will be used only if they are not overridden by the virtual host
settings.</p>
</div></div>
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