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 <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>

 <H2>Name-based vs. IP-based virtual hosts</H2>

 <P>While the approach with IP-based virtual hosts works very well,
 it is not the most elegant solution, because a dedicated IP address
 is needed for every virtual host and it is hard to implement on some
 machines. The <CODE>HTTP/1.1</CODE> protocol contains 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 traditional
 IP-address-per-hostname method.</P>

 <P>The benefits of using the new name-based virtual host support is a
 practically unlimited number of servers, ease of configuration and use, and
 requires no additional hardware or software.
 The main disadvantage is that the client must support this part of the
 protocol. The latest versions of most browsers do, but there are still
 old browsers in use who do not. This can cause problems, although a possible
 solution is addressed below.</P>

 <H2>Using non-IP Virtual Hosts</H2>

 <P>Using the new 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>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>


 <PRE>
     NameVirtualHost 111.22.33.44

     &lt;VirtualHost 111.22.33.44&gt;
     ServerName www.domain.tld
     DocumentRoot /www/domain
     &lt;/VirtualHost&gt;

     &lt;VirtualHost 111.22.33.44&gt;
     ServerName www.otherdomain.tld
     DocumentRoot /www/otherdomain
     &lt;/VirtualHost&gt;
 </PRE>

 <P>Of course, any additional directives can (and should) be placed
 into the <CODE>&lt;VirtualHost&gt;</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>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 &lt;VirtualHost&gt;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 to use 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 &lt;VirtualHost&gt; section for
 <EM>every</EM> server (hostname) you want to maintain on your server.

 <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 &lt;VirtualHost&gt; section. For
 example:</P>

 <PRE>
     ServerAlias domain.tld *.domain.tld
 </PRE>

 <P>Note that you can use <CODE>*</CODE> and <CODE>?</CODE> as wild-card
 characters.</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>

 <H2>Compatibility with Older Browsers</H2>

 <P>As mentioned earlier, there are still some clients in use 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>

 <P>There is a possible workaround with the
 <A HREF="../mod/core.html#serverpath"><CODE>ServerPath</CODE></A>
 directive, albeit a slightly cumbersome one:</P>

 <P>Example configuration:

 <PRE>
     NameVirtualHost 111.22.33.44

     &lt;VirtualHost 111.22.33.44&gt;
     ServerName www.domain.tld
     ServerPath /domain
     DocumentRoot /web/domain
     &lt;/VirtualHost&gt;
 </PRE>

 <P>What does this mean? It means that a request for any URI beginning
 with "<SAMP>/domain</SAMP>" will be served from the virtual host
 <SAMP>www.domain.tld</SAMP> This means that the pages can be accessed as
 <CODE>http://www.domain.tld/domain/</CODE> for all clients, although
 clients sending a <SAMP>Host:</SAMP> 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 <SAMP>http://www.domain.tld/domain/</SAMP>
 Then, in the virtual host's pages, be sure to use either purely
 relative links (<EM>e.g.</EM>, "<SAMP>file.html</SAMP>" or
 "<SAMP>../icons/image.gif</SAMP>" or links containing the prefacing
 <SAMP>/domain/</SAMP>
 (<EM>e.g.</EM>, "<SAMP>http://www.domain.tld/domain/misc/file.html</SAMP>" or
 "<SAMP>/domain/misc/file.html</SAMP>").</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>

 <P>See also: <A HREF="examples.html#serverpath">ServerPath configuration
 example</A></P>

 <!--#include virtual="footer.html" -->
 </BODY>
 </HTML>
	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
	<HTML><HEAD>
	<TITLE>Apache name-based Virtual Hosts</TITLE>
	</HEAD>

	<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
	<BODY
	BGCOLOR="#FFFFFF"
	TEXT="#000000"
	LINK="#0000FF"
	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>

	<H2>Name-based vs. IP-based virtual hosts</H2>

	<P>While the approach with IP-based virtual hosts works very well,
	it is not the most elegant solution, because a dedicated IP address
	is needed for every virtual host and it is hard to implement on some
	machines. The <CODE>HTTP/1.1</CODE> protocol contains 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 traditional
	IP-address-per-hostname method.</P>

	<P>The benefits of using the new name-based virtual host support is a
	practically unlimited number of servers, ease of configuration and use, and
	requires no additional hardware or software.
	The main disadvantage is that the client must support this part of the
	protocol. The latest versions of most browsers do, but there are still
	old browsers in use who do not. This can cause problems, although a possible
	solution is addressed below.</P>

	<H2>Using non-IP Virtual Hosts</H2>

	<P>Using the new 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>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>



	<PRE>
	NameVirtualHost 111.22.33.44

	<VirtualHost 111.22.33.44>
	ServerName www.domain.tld
	DocumentRoot /www/domain
	</VirtualHost>

	<VirtualHost 111.22.33.44>
	ServerName www.otherdomain.tld
	DocumentRoot /www/otherdomain
	</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>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 to use 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>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>Note that you can use <CODE>*</CODE> and <CODE>?</CODE> as wild-card
	characters.</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>

	<H2>Compatibility with Older Browsers</H2>

	<P>As mentioned earlier, there are still some clients in use 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>

	<P>There is a possible workaround with the
	<A HREF="../mod/core.html#serverpath"><CODE>ServerPath</CODE></A>
	directive, albeit a slightly cumbersome one:</P>

	<P>Example configuration:

	<PRE>
	NameVirtualHost 111.22.33.44

	<VirtualHost 111.22.33.44>
	ServerName www.domain.tld
	ServerPath /domain
	DocumentRoot /web/domain
	</VirtualHost>
	</PRE>

	<P>What does this mean? It means that a request for any URI beginning
	with "<SAMP>/domain</SAMP>" will be served from the virtual host
	<SAMP>www.domain.tld</SAMP> This means that the pages can be accessed as
	<CODE>http://www.domain.tld/domain/</CODE> for all clients, although
	clients sending a <SAMP>Host:</SAMP> 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 <SAMP>http://www.domain.tld/domain/</SAMP>
	Then, in the virtual host's pages, be sure to use either purely
	relative links (<EM>e.g.</EM>, "<SAMP>file.html</SAMP>" or
	"<SAMP>../icons/image.gif</SAMP>" or links containing the prefacing
	<SAMP>/domain/</SAMP>
	(<EM>e.g.</EM>, "<SAMP>http://www.domain.tld/domain/misc/file.html</SAMP>" or
	"<SAMP>/domain/misc/file.html</SAMP>").</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>

	<P>See also: <A HREF="examples.html#serverpath">ServerPath configuration
	example</A></P>

	<!--#include virtual="footer.html" -->
	</BODY>
	</HTML>