docs/manual/vhosts/name-based.html.en - httpd - Git at Google

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 <title>Name-based Virtual Host Support - Apache HTTP Server</title>
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 <body id="manual-page"><div id="page-header">
 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
 <p class="apache">Apache HTTP Server Version 2.0</p>
 <img alt="" src="../images/feather.gif" /></div>
 <div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
 <div id="path">
 <a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs-project/">Documentation</a> &gt; <a href="../">Version 2.0</a> &gt; <a href="./">Virtual Hosts</a></div><div id="page-content"><div id="preamble"><h1>Name-based Virtual Host Support</h1>

 	<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="#using">Using Name-based Virtual Hosts</a></li>
 <li><img alt="" src="../images/down.gif" /> <a href="#compat">Compatibility with Older Browsers</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><li><a href="examples.html#serverpath">ServerPath configuration example</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="namevip" id="namevip">Name-based vs. IP-based Virtual Hosts</a></h2>

 	<p>IP-based virtual hosts 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.  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>Some ancient clients are not compatible with name-based virtual
 		hosting.  For name-based virtual hosting to work, the client must send
 		the HTTP Host header.  This is required by HTTP/1.1, and is
 		implemented by all modern HTTP/1.0 browsers as an extension.  If you
 		need to support obsolete clients and still use name-based virtual
 		hosting, a possible technique is discussed at the end of this
 		document.</li>

 		<li>Name-based virtual hosting cannot be used with SSL secure servers
 		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="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#serverpath">ServerPath</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 for the hosts.  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>NameVirtualHost</code>.  Note that mentioning an IP address in a
 	<code>NameVirtualHost</code> directive does not automatically make the
 	server listen 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>

 	<p>The next step is to create a <code class="directive"><a href="../mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code> block for
 	each different host that you would like to serve.  The argument to the
 	<code>&lt;VirtualHost&gt;</code> directive should be the same as the
 	argument to the <code>NameVirtualHost</code> directive (ie, an IP
 	address, or <code>*</code> for all addresses).  Inside each
 	<code>&lt;VirtualHost&gt;</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>
 	If you are adding virtual hosts to an existing web server, you
 	must also create a &lt;VirtualHost&gt; block for the existing host.
 	The <code>ServerName</code> and <code>DocumentRoot</code> included in
 	this virtual host should be the same as the global
 	<code>ServerName</code> and <code>DocumentRoot</code>.  List this
 	virtual host first in the configuration file so that it will act as
 	the default host.
     </div>

 	<p>For example, suppose that you are serving the domain
 	<code>www.domain.tld</code> and you wish to add the virtual host
 	<code>www.otherdomain.tld</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 *<br />
     <br />
     &lt;VirtualHost *&gt;<br />
     <span class="indent">
     ServerName www.domain.tld<br />
     ServerAlias domain.tld *.domain.tld<br />
     DocumentRoot /www/domain<br />
     </span>
     &lt;/VirtualHost&gt;<br />
     <br />
     &lt;VirtualHost *&gt;<br />
     <span class="indent">ServerName www.otherdomain.tld<br />
     DocumentRoot /www/otherdomain<br />
     </span>
     &lt;/VirtualHost&gt;<br />
 	</code></p></div>

 	<p>You can alternatively specify an explicit IP address in place of
 	the * in both the <code>NameVirtualHost</code> and
 	<code>&lt;VirtualHost&gt;</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 &lt;VirtualHost&gt; section. For
 	example in the first &lt;VirtualHost&gt; 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 domain.tld *.domain.tld
 	</code></p></div>

 	<p>then requests for all hosts in the <code>domain.tld</code> domain
 	will be served by the <code>www.domain.tld</code> virtual host.  The
 	wildcard characters * and ? can be used to match names.  Of course,
 	you can't just make up names and place them in <code>ServerName</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>&lt;VirtualHost&gt;</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>&lt;VirtualHost&gt;</code> container)
 	will be used only if they are not overriden by the virtual host
 	settings.</p>

 	<p>Now when a request arrives, the server will first check if it is
 	using an IP address that matches the <code>NameVirtualHost</code>.  If
 	it is, then it will look at each <code>&lt;VirtualHost&gt;</code>
 	section with a matching IP address and try to find one where the
 	<code>ServerName</code> or <code>ServerAlias</code> matches the
 	requested hostname.  If it finds one, then it uses the configuration
 	for that server.  If no matching virtual host is found, then
 	<strong>the first listed virtual host</strong> that matches the IP
 	address will be used.</p>

 	<p>As a consequence, the first listed virtual host is the
 	<em>default</em> virtual host.  The <code>DocumentRoot</code> from the
 	<em>main server</em> will <strong>never</strong> be used when an IP
 	address matches the <code>NameVirtualHost</code> directive.  If you
 	would like to have a special configuration for requests that do not
 	match any particular virtual host, simply put that configuration in a
 	<code>&lt;VirtualHost&gt;</code> container and list it first in the
 	configuration file.</p>

 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 <div class="section">
 <h2><a name="compat" id="compat">Compatibility with Older Browsers</a></h2>

     <p>As mentioned earlier, there are some clients
     who do not send the required data for the name-based virtual
     hosts to work properly. These clients will always be sent the
     pages from the first virtual host listed for that IP address
     (the <cite>primary</cite> name-based virtual host).</p>

     <div class="note"><h3>How much older?</h3>
     Please note that when we say older, we really do mean older. You are
     very unlikely to encounter one of these browsers in use today. All
     current versions of any browser send the <code>Host</code> header as
     required for name-based virtual hosts.
     </div>

     <p>There is a possible workaround with the <code class="directive"><a href="../mod/core.html#serverpath">ServerPath</a></code>
     directive, albeit a slightly cumbersome one:</p>

     <p>Example configuration:</p>

     <div class="example"><p><code>
     NameVirtualHost 111.22.33.44<br />
     <br />
     &lt;VirtualHost 111.22.33.44&gt;<br />
     <span class="indent">
     ServerName www.domain.tld<br />
     ServerPath /domain<br />
     DocumentRoot /web/domain<br />
     </span>
     &lt;/VirtualHost&gt;<br />
  	  </code></p></div>

     <p>What does this mean? It means that a request for any URI
     beginning with "<code>/domain</code>" will be served from the
     virtual host <code>www.domain.tld</code> This means that the
     pages can be accessed as
     <code>http://www.domain.tld/domain/</code> for all clients,
     although clients sending a <code>Host:</code> header can also
     access it as <code>http://www.domain.tld/</code>.</p>

     <p>In order to make this work, put a link on your primary
     virtual host's page to
     <code>http://www.domain.tld/domain/</code> Then, in the virtual
     host's pages, be sure to use either purely relative links
     (<em>e.g.</em>, "<code>file.html</code>" or
     "<code>../icons/image.gif</code>" or links containing the
     prefacing <code>/domain/</code> (<em>e.g.</em>,
     "<code>http://www.domain.tld/domain/misc/file.html</code>" or
     "<code>/domain/misc/file.html</code>").</p>

     <p>This requires a bit of discipline, but adherence to these
     guidelines will, for the most part, ensure that your pages will
     work with all browsers, new and old.</p>

 </div></div>
 <div id="footer">
 <p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache HTTP Server Documentation Project</a></p>
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	<title>Name-based Virtual Host Support - Apache HTTP Server</title>
	<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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	<body id="manual-page"><div id="page-header">
	<p class="menu"><a href="../mod/">Modules</a> \| <a href="../mod/directives.html">Directives</a> \| <a href="../faq/">FAQ</a> \| <a href="../glossary.html">Glossary</a> \| <a href="../sitemap.html">Sitemap</a></p>
	<p class="apache">Apache HTTP Server Version 2.0</p>
	<img alt="" src="../images/feather.gif" /></div>
	<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
	<div id="path">
	<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="../">Version 2.0</a> > <a href="./">Virtual Hosts</a></div><div id="page-content"><div id="preamble"><h1>Name-based Virtual Host Support</h1>

	<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="#using">Using Name-based Virtual Hosts</a></li>
	<li><img alt="" src="../images/down.gif" /> <a href="#compat">Compatibility with Older Browsers</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><li><a href="examples.html#serverpath">ServerPath configuration example</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="namevip" id="namevip">Name-based vs. IP-based Virtual Hosts</a></h2>

	<p>IP-based virtual hosts 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. 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>Some ancient clients are not compatible with name-based virtual
	hosting. For name-based virtual hosting to work, the client must send
	the HTTP Host header. This is required by HTTP/1.1, and is
	implemented by all modern HTTP/1.0 browsers as an extension. If you
	need to support obsolete clients and still use name-based virtual
	hosting, a possible technique is discussed at the end of this
	document.</li>

	<li>Name-based virtual hosting cannot be used with SSL secure servers
	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="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#serverpath">ServerPath</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 for the hosts. 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>NameVirtualHost</code>. Note that mentioning an IP address in a
	<code>NameVirtualHost</code> directive does not automatically make the
	server listen 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>

	<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><VirtualHost></code> directive should be the same as the
	argument to the <code>NameVirtualHost</code> directive (ie, an IP
	address, or <code>*</code> for all addresses). Inside each
	<code><VirtualHost></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>
	If you are adding virtual hosts to an existing web server, you
	must also create a <VirtualHost> block for the existing host.
	The <code>ServerName</code> and <code>DocumentRoot</code> included in
	this virtual host should be the same as the global
	<code>ServerName</code> and <code>DocumentRoot</code>. List this
	virtual host first in the configuration file so that it will act as
	the default host.
	</div>

	<p>For example, suppose that you are serving the domain
	<code>www.domain.tld</code> and you wish to add the virtual host
	<code>www.otherdomain.tld</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 *<br />
	<br />
	<VirtualHost *><br />
	<span class="indent">
	ServerName www.domain.tld<br />
	ServerAlias domain.tld *.domain.tld<br />
	DocumentRoot /www/domain<br />
	</span>
	</VirtualHost><br />
	<br />
	<VirtualHost *><br />
	<span class="indent">ServerName www.otherdomain.tld<br />
	DocumentRoot /www/otherdomain<br />
	</span>
	</VirtualHost><br />
	</code></p></div>

	<p>You can alternatively specify an explicit IP address in place of
	the * in both the <code>NameVirtualHost</code> and
	<code><VirtualHost></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 <VirtualHost> section. For
	example in the first <VirtualHost> 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 domain.tld *.domain.tld
	</code></p></div>

	<p>then requests for all hosts in the <code>domain.tld</code> domain
	will be served by the <code>www.domain.tld</code> virtual host. The
	wildcard characters * and ? can be used to match names. Of course,
	you can't just make up names and place them in <code>ServerName</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><VirtualHost></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><VirtualHost></code> container)
	will be used only if they are not overriden by the virtual host
	settings.</p>

	<p>Now when a request arrives, the server will first check if it is
	using an IP address that matches the <code>NameVirtualHost</code>. If
	it is, then it will look at each <code><VirtualHost></code>
	section with a matching IP address and try to find one where the
	<code>ServerName</code> or <code>ServerAlias</code> matches the
	requested hostname. If it finds one, then it uses the configuration
	for that server. If no matching virtual host is found, then
	<strong>the first listed virtual host</strong> that matches the IP
	address will be used.</p>

	<p>As a consequence, the first listed virtual host is the
	<em>default</em> virtual host. The <code>DocumentRoot</code> from the
	<em>main server</em> will <strong>never</strong> be used when an IP
	address matches the <code>NameVirtualHost</code> directive. If you
	would like to have a special configuration for requests that do not
	match any particular virtual host, simply put that configuration in a
	<code><VirtualHost></code> container and list it first in the
	configuration file.</p>

	</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
	<div class="section">
	<h2><a name="compat" id="compat">Compatibility with Older Browsers</a></h2>

	<p>As mentioned earlier, there are some clients
	who do not send the required data for the name-based virtual
	hosts to work properly. These clients will always be sent the
	pages from the first virtual host listed for that IP address
	(the <cite>primary</cite> name-based virtual host).</p>

	<div class="note"><h3>How much older?</h3>
	Please note that when we say older, we really do mean older. You are
	very unlikely to encounter one of these browsers in use today. All
	current versions of any browser send the <code>Host</code> header as
	required for name-based virtual hosts.
	</div>

	<p>There is a possible workaround with the <code class="directive"><a href="../mod/core.html#serverpath">ServerPath</a></code>
	directive, albeit a slightly cumbersome one:</p>

	<p>Example configuration:</p>

	<div class="example"><p><code>
	NameVirtualHost 111.22.33.44<br />
	<br />
	<VirtualHost 111.22.33.44><br />
	<span class="indent">
	ServerName www.domain.tld<br />
	ServerPath /domain<br />
	DocumentRoot /web/domain<br />
	</span>
	</VirtualHost><br />
	</code></p></div>

	<p>What does this mean? It means that a request for any URI
	beginning with "<code>/domain</code>" will be served from the
	virtual host <code>www.domain.tld</code> This means that the
	pages can be accessed as
	<code>http://www.domain.tld/domain/</code> for all clients,
	although clients sending a <code>Host:</code> header can also
	access it as <code>http://www.domain.tld/</code>.</p>

	<p>In order to make this work, put a link on your primary
	virtual host's page to
	<code>http://www.domain.tld/domain/</code> Then, in the virtual
	host's pages, be sure to use either purely relative links
	(<em>e.g.</em>, "<code>file.html</code>" or
	"<code>../icons/image.gif</code>" or links containing the
	prefacing <code>/domain/</code> (<em>e.g.</em>,
	"<code>http://www.domain.tld/domain/misc/file.html</code>" or
	"<code>/domain/misc/file.html</code>").</p>

	<p>This requires a bit of discipline, but adherence to these
	guidelines will, for the most part, ensure that your pages will
	work with all browsers, new and old.</p>

	</div></div>
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