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<title>Apache IP-based Virtual Host Support - Apache HTTP Server</title>
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<p class="apache">Apache HTTP Server Version 2.2</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 2.2</a> > <a href="./">Virtual Hosts</a></div><div id="page-content"><div id="preamble"><h1>Apache IP-based Virtual Host Support</h1>
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<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#requirements">System requirements</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#howto">How to set up Apache</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#multiple">Setting up multiple daemons</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#single">Setting up a single daemon
with virtual hosts</a></li>
</ul><h3>See also</h3><ul class="seealso"><li>
<a href="name-based.html">Name-based Virtual Hosts Support</a>
</li></ul></div>
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<div class="section">
<h2><a name="requirements" id="requirements">System requirements</a></h2>
<p>As the term <cite>IP-based</cite> indicates, the server
<strong>must have a different IP address for each IP-based
virtual host</strong>. This can be achieved by the machine
having several physical network connections, or by use of
virtual interfaces which are supported by most modern operating
systems (see system documentation for details, these are
frequently called "ip aliases", and the "ifconfig" command is
most commonly used to set them up).</p>
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<div class="section">
<h2><a name="howto" id="howto">How to set up Apache</a></h2>
<p>There are two ways of configuring apache to support multiple
hosts. Either by running a separate <code class="program"><a href="../programs/httpd.html">httpd</a></code> daemon for
each hostname, or by running a single daemon which supports all the
virtual hosts.</p>
<p>Use multiple daemons when:</p>
<ul>
<li>There are security partitioning issues, such as company1
does not want anyone at company2 to be able to read their
data except via the web. In this case you would need two
daemons, each running with different <code class="directive"><a href="../mod/mpm_common.html#user">User</a></code>, <code class="directive"><a href="../mod/mpm_common.html#group">Group</a></code>, <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code>, and <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code> settings.</li>
<li>You can afford the memory and file descriptor
requirements of listening to every IP alias on the
machine. It's only possible to <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code> to the "wildcard"
address, or to specific addresses. So if you have a need to
listen to a specific address for whatever reason, then you
will need to listen to all specific addresses. (Although one
<code class="program"><a href="../programs/httpd.html">httpd</a></code> could listen to N-1 of the addresses, and another could
listen to the remaining address.)</li>
</ul>
<p>Use a single daemon when:</p>
<ul>
<li>Sharing of the httpd configuration between virtual hosts
is acceptable.</li>
<li>The machine services a large number of requests, and so
the performance loss in running separate daemons may be
significant.</li>
</ul>
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<div class="section">
<h2><a name="multiple" id="multiple">Setting up multiple daemons</a></h2>
<p>Create a separate <code class="program"><a href="../programs/httpd.html">httpd</a></code> installation for each
virtual host. For each installation, use the <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code> directive in the
configuration file to select which IP address (or virtual host)
that daemon services. e.g.</p>
<div class="example"><p><code>
Listen www.smallco.com:80
</code></p></div>
<p>It is recommended that you use an IP address instead of a
hostname (see <a href="../dns-caveats.html">DNS caveats</a>).</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="single" id="single">Setting up a single daemon
with virtual hosts</a></h2>
<p>For this case, a single <code class="program"><a href="../programs/httpd.html">httpd</a></code> will service
requests for the main server and all the virtual hosts. The <code class="directive"><a href="../mod/core.html#virtualhost">VirtualHost</a></code> directive
in the configuration file is used to set the values of <code class="directive"><a href="../mod/core.html#serveradmin">ServerAdmin</a></code>, <code class="directive"><a href="../mod/core.html#servername">ServerName</a></code>, <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>, <code class="directive"><a href="../mod/core.html#errorlog">ErrorLog</a></code> and <code class="directive"><a href="../mod/mod_log_config.html#transferlog">TransferLog</a></code>
or <code class="directive"><a href="../mod/mod_log_config.html#customlog">CustomLog</a></code>
configuration directives to different values for each virtual
host. e.g.</p>
<div class="example"><p><code>
<VirtualHost www.smallco.com><br />
ServerAdmin webmaster@mail.smallco.com<br />
DocumentRoot /groups/smallco/www<br />
ServerName www.smallco.com<br />
ErrorLog /groups/smallco/logs/error_log<br />
TransferLog /groups/smallco/logs/access_log<br />
</VirtualHost><br />
<br />
<VirtualHost www.baygroup.org><br />
ServerAdmin webmaster@mail.baygroup.org<br />
DocumentRoot /groups/baygroup/www<br />
ServerName www.baygroup.org<br />
ErrorLog /groups/baygroup/logs/error_log<br />
TransferLog /groups/baygroup/logs/access_log<br />
</VirtualHost>
</code></p></div>
<p>It is recommended that you use an IP address instead of a
hostname (see <a href="../dns-caveats.html">DNS caveats</a>).</p>
<p>Almost <strong>any</strong> configuration directive can be
put in the VirtualHost directive, with the exception of
directives that control process creation and a few other
directives. To find out if a directive can be used in the
VirtualHost directive, check the <a href="../mod/directive-dict.html#Context">Context</a> using the
<a href="../mod/directives.html">directive index</a>.</p>
<p><code class="directive"><a href="../mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code>
may be used inside a
VirtualHost directive if the <a href="../suexec.html">suEXEC
wrapper</a> is used.</p>
<p><em>SECURITY:</em> When specifying where to write log files,
be aware of some security risks which are present if anyone
other than the user that starts Apache has write access to the
directory where they are written. See the <a href="../misc/security_tips.html">security tips</a> document
for details.</p>
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