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<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE manualpage SYSTEM "../style/manualpage.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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<manualpage metafile="ip-based.xml.meta">
<parentdocument href="./">Virtual Hosts</parentdocument>
<title>Apache IP-based Virtual Host Support</title>
<seealso>
<a href="name-based.html">Name-based Virtual Hosts Support</a>
</seealso>
<section id="explanation"><title>What is IP-based virtual hosting</title>
<p>IP-based virtual hosting is a method to apply different directives
based on the IP address and port a request is received on. Most commonly,
this is used to serve different websites on different ports or interfaces.</p>
<p>In many cases, <a href="name-based.html">name-based
virtual hosts</a> are more convenient, because they allow
many virtual hosts to share a single address/port.
See <a href="name-based.html#namevip">Name-based vs. IP-based
Virtual Hosts</a> to help you decide. </p>
</section>
<section id="requirements"><title>System requirements</title>
<p>As the term <cite>IP-based</cite> indicates, the server
<strong>must have a different IP address/port combination 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), and/or using multiple
port numbers.</p>
<p> In the terminology of Apache HTTP Server, using a single IP address
but multiple TCP ports, is also IP-based virtual hosting.</p>
</section>
<section id="howto"><title>How to set up Apache</title>
<p>There are two ways of configuring apache to support multiple
hosts. Either by running a separate <program>httpd</program> 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 <directive
module="mpm_common">User</directive>, <directive
module="mpm_common">Group</directive>, <directive
module="mpm_common">Listen</directive>, and <directive
module="core">ServerRoot</directive> 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 <directive
module="mpm_common">Listen</directive> 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
<program>httpd</program> 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>
</section>
<section id="multiple"><title>Setting up multiple daemons</title>
<p>Create a separate <program>httpd</program> installation for each
virtual host. For each installation, use the <directive
module="mpm_common">Listen</directive> directive in the
configuration file to select which IP address (or virtual host)
that daemon services. e.g.</p>
<example>
Listen 192.0.2.100:80
</example>
<p>It is recommended that you use an IP address instead of a
hostname (see <a href="../dns-caveats.html">DNS caveats</a>).</p>
</section>
<section id="single"><title>Setting up a single daemon
with virtual hosts</title>
<p>For this case, a single <program>httpd</program> will service
requests for the main server and all the virtual hosts. The <directive
module="core">VirtualHost</directive> directive
in the configuration file is used to set the values of <directive
module="core">ServerAdmin</directive>, <directive
module="core">ServerName</directive>, <directive
module="core">DocumentRoot</directive>, <directive
module="core">ErrorLog</directive> and <directive
module="mod_log_config">TransferLog</directive>
or <directive module="mod_log_config">CustomLog</directive>
configuration directives to different values for each virtual
host. e.g.</p>
<example>
<VirtualHost 172.20.30.40:80><br />
ServerAdmin webmaster@www1.example.com<br />
DocumentRoot /www/vhosts/www1<br />
ServerName www1.example.com<br />
ErrorLog /www/logs/www1/error_log<br />
CustomLog /www/logs/www1/access_log combined<br />
</VirtualHost><br />
<br />
<VirtualHost 172.20.30.50:80><br />
ServerAdmin webmaster@www2.example.org<br />
DocumentRoot /www/vhosts/www2<br />
ServerName www2.example.org<br />
ErrorLog /www/logs/www2/error_log<br />
CustomLog /www/logs/www2/access_log combined<br />
</VirtualHost>
</example>
<p>It is recommended that you use an IP address instead of a
hostname in the <VirtualHost> directive
(see <a href="../dns-caveats.html">DNS caveats</a>).</p>
<p> Specific IP addresses or ports have precedence over their wildcard
equivalents, and any virtual host that matches has precedence over
the servers base configuration.</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><directive module="mod_suexec">SuexecUserGroup</directive>
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>
</section>
</manualpage>
|
