slive 01/10/22 13:15:26 Modified: htdocs/manual/vhosts name-based.html.en Log: Refresh of the name vhosting docs. Reviewed by: Allan Liska Revision Changes Path 1.17 +151 -102 httpd-docs-1.3/htdocs/manual/vhosts/name-based.html.en Index: name-based.html.en =================================================================== RCS file: /home/cvs/httpd-docs-1.3/htdocs/manual/vhosts/name-based.html.en,v retrieving revision 1.16 retrieving revision 1.17 diff -u -d -b -u -r1.16 -r1.17 --- name-based.html.en 2001/10/08 01:37:37 1.16 +++ name-based.html.en 2001/10/22 20:15:26 1.17 @@ -3,9 +3,7 @@ <html xmlns="http://www.w3.org/1999/xhtml";> <head> - <meta name="generator" content="HTML Tidy, see www.w3.org" /> - - <title>Apache name-based Virtual Hosts</title> + <title>Name-based Virtual Hosts</title> </head> <!-- Background white, links blue (unvisited), navy (visited), red (active) --> @@ -13,50 +11,103 @@ vlink="#000080" alink="#FF0000"> <!--#include virtual="header.html" --> - <h1 align="CENTER">Apache name-based Virtual Host Support</h1> - <strong>See Also:</strong> <a href="ip-based.html">IP-based - Virtual Host Support</a> - <hr /> + <h1 align="CENTER">Name-based Virtual Host Support</h1> - <h2>Name-based vs. IP-based virtual hosts</h2> +<p>This document describes when and how to use name-based virtual hosts.</p> - <p>Early versions of HTTP (like many other protocols, e.g. FTP) - required a different IP address for each virtual host on the - server. On some platforms this can limit the number of virtual - hosts you can run, and because there are concerns about the - availability of IP addresses it is strongly discouraged by the - registraries (ARIN, RIPE, and APNIC).</p> +<ul> +<li><a href="#namevip">Name-based vs. IP-based Virtual Hosts</a></li> +<li><a href="#using">Using Name-based Virtual Hosts</a></li> +<li><a href="#compat">Compatibility With Older Browsers</a></li> +</ul> - <p>The <code>HTTP/1.1</code> protocol, and a common extension - to <code>HTTP/1.0</code>, includes a method for the server to - identify what name it is being addressed as. Apache 1.1 and - later support this approach as well as the old - IP-address-per-hostname method.</p> +<p>See also: <a href="examples.html">Virtual Host examples for common +setups</a>, <a href="ip-based.html">IP-based Virtual Host Support</a>, +<a href="details.html">An In-Depth Discussion of Virtual Host +Matching</a>, and <a href="mass.html">Dynamically configured mass +virtual hosting</a>.</p> - <p>The benefits of using the name-based virtual hosts is a - practically unlimited number of servers, ease of configuration - and use, and it requires no additional hardware or software. - The main disadvantage is that the client must support this part - of the protocol. Almost all browsers do, but there are still - tiny numbers of very old browsers in use which do not. This can - cause problems, although a possible solution is addressed - below.</p> +<hr /> - <h2>Using name-based virtual hosts</h2> +<h2><a name="namevip">Name-based vs. IP-based Virtual Hosts</a></h2> - <p>Using name-based virtual hosts is quite easy, and - superficially looks like the old method. The notable difference - between IP-based and name-based virtual host configuration is - the <a - href="../mod/core.html#namevirtualhost"><code>NameVirtualHost</code></a> - directive which specifies an IP address that should be used as - a target for name-based virtual hosts.</p> +<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>For example, suppose that both <samp>www.domain.tld</samp> - and <samp>www.otherdomain.tld</samp> point at the IP address - <samp>111.22.33.44</samp>. Then you simply add to one of the - Apache configuration files (most likely <code>httpd.conf</code> - or <code>srm.conf</code>) code similar to the following:</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> + +<h2><a name="using">Using Name-based Virtual Hosts</a></h2> + +<table border="1"> +<tr><td align="top"> +<strong>Related Directives</strong><br><br> + +<a href="mod/core.html#documentroot">DocumentRoot</a><br /> +<a href="mod/core.html#namevirtualhost">NameVirtualHost</a><br /> +<a href="mod/core.html#serveralias">ServerAlias</a><br /> +<a href="mod/core.html#servername">ServerName</a><br /> +<a href="mod/core.html#serverpath">ServerPath</a><br /> +<a href="mod/core.html#virtualhost">VirtualHost</a><br /> +</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 <a +href="../mod/core.html#namevirtualhost">NameVirtualHost</a> 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. + +<p>The next step is to create a <a +href="../mod/core.html#virtualhost"><VirtualHost></a> 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 <a +href="../mod/core.html#servername">ServerName</a> directive to +designate which host is served and a <a +href="../mod/core.html#documentroot">DocumentRoot</a> directive to +show where in the filesystem the content for that host lives.</p> + +<p>For example, suppose that both <samp>www.domain.tld</samp> and +<samp>www.otherdomain.tld</samp> point at the IP address +<samp>111.22.33.44</samp>. Then you simply add the following +to <code>httpd.conf</code>:</p> + <pre> NameVirtualHost 111.22.33.44 @@ -71,64 +122,62 @@ </VirtualHost> </pre> - <p>Of course, any additional directives can (and should) be - placed into the <code><VirtualHost></code> section. To - make this work, all that is needed is to make sure that the - names <samp>www.domain.tld</samp> and - <samp>www.otherdomain.tld</samp> are pointing to the IP address - <samp>111.22.33.44</samp></p> +<p>In the simplest case, the IP address <code>111.22.44.33</code> can be +replaced by <code>*</code> to match all IP addresses for your server.</p> - <p>Note: When you specify an IP address in a - <code>NameVirtualHost</code> directive then requests to that IP - address will only ever be served by matching - <VirtualHost>s. The "main server" will - <strong>never</strong> be served from the specified IP address. - If you start to use virtual hosts you should stop using the - "main server" as an independent server and rather use it as a - place for configuration directives that are common for all your - virtual hosts. In other words, you should add a - <VirtualHost> section for <em>every</em> server - (hostname) you want to maintain on your server.</p> +<p>Many servers want to be accessible by more than one name. This is +possible with the <a +href="../mod/core.html#serveralias"><code>ServerAlias</code></a> +directive, placed inside the <VirtualHost> section. For +example if you add this to the first <VirtualHost> block +above</p> - <p>In Apache 1.3.13 and later you can specify the - <code>NameVirtualHost</code> IP address as the wildcard - <code>*</code> which matches any IP address not covered by more - specific virtual host directive(s). This is useful for - configuring a server whose IP address you do not know in - advance, e.g. because it has a dynamically configured IP - address or because it is part of a load-balanced cluster in - which every machine shares the same configuration file.</p> +<blockquote><code> +ServerAlias domain.tld *.domain.tld +</code></blockquote> - <p>Additionally, many servers may wish to be accessible by more - than one name. For example, the example server might want to be - accessible as <code>domain.tld</code>, or - <code>www2.domain.tld</code>, assuming the IP addresses pointed - to the same server. In fact, one might want it so that all - addresses at <code>domain.tld</code> were picked up by the - server. This is possible with the <a - href="../mod/core.html#serveralias"><code>ServerAlias</code></a> - directive, placed inside the <VirtualHost> section. For - example:</p> -<pre> - ServerAlias domain.tld *.domain.tld -</pre> +<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 the IP address in the +<code>NameVirtualHost</code> directive.</p> - <p>Note that you can use <code>*</code> and <code>?</code> as - wild-card characters.</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-dist.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>You also might need <code>ServerAlias</code> if you are - serving local users who do not always include the domain name. - For example, if local users are familiar with typing "www" or - "www.foobar" then you will need to add <code>ServerAlias www - www.foobar</code>. It isn't possible for the server to know - what domain the client uses for their name resolution because - the client doesn't provide that information in the request. The - <code>ServerAlias</code> directive is generally a way to have - different hostnames pointing to the same virtual host.</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> - <h2>Compatibility with Older Browsers</h2> +<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> - <p>As mentioned earlier, there are still some clients in use +<h2><a name="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
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