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This document describes when and how to use name-based virtual hosts.
See also: Virtual Host examples for common setups, IP-based Virtual Host Support, An In-Depth Discussion of Virtual Host Matching, and Dynamically configured mass virtual hosting.
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.
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:
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 NameVirtualHost
directive. In the normal case where any and all IP addresses on the server
should be used, you can use
* as the argument to
NameVirtualHost * will work only in
version 1.3.13 and later.) Note that mentioning an IP address in a
NameVirtualHost directive does not automatically make the server
listen to that IP address. See Setting which addresses and
ports Apache uses for more details. In addition, any IP address specified
here must be associated with a network interface on the server.
The next step is to create a <VirtualHost>
block for each different host that you would like to serve. The argument to the
<VirtualHost> directive should be the same as the argument to
NameVirtualHost directive (ie, an IP address, or
for all addresses). Inside each
<VirtualHost> block, you will
need at minimum a ServerName
directive to designate which host is served and a DocumentRoot
directive to show where in the filesystem the content for that host lives.
If you are adding virtual hosts to an existing web server, you must also
create a <VirtualHost> block for the existing host. The
DocumentRoot included in this virtual
host should be the same as the global
DocumentRoot. List this virtual host first in the configuration
file so that it will act as the default host.
For example, suppose that you are serving the domain
www.domain.tld and you wish to add the virtual host
www.otherdomain.tld, which points at the same IP address. Then you
simply add the following to
NameVirtualHost * <VirtualHost *> ServerName www.domain.tld DocumentRoot /www/domain </VirtualHost> <VirtualHost *> ServerName www.otherdomain.tld DocumentRoot /www/otherdomain </VirtualHost>
You can alternatively specify an explicit IP address in place of the * in
directives. The IP address is required in version 1.3.12 and earlier.
Many servers want to be accessible by more than one name. This is possible
directive, placed inside the <VirtualHost> section. For example if you add
this to the first <VirtualHost> block above
ServerAlias domain.tld *.domain.tld
then requests for all hosts in the
domain.tld domain will be
served by the
www.domain.tld 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
ServerAlias. You must
first have your DNS server properly configured to map those names to an IP
address associated with your server.
Finally, you can fine-tune the configuration of the virtual hosts by placing
other directives inside the
<VirtualHost> 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 Context
of the directive. Configuration directives set in the main server
context (outside any
<VirtualHost> container) will be
used only if they are not overriden by the virtual host settings.
Now when a request arrives, the server will first check if it is using an IP
address that matches the
NameVirtualHost. If it is, then it will
look at each
<VirtualHost> section with a matching IP address
and try to find one where the
ServerAlias matches the requested hostname. If it finds one, then
it uses the configuration for that server. If no matching virtual host is found,
then the first listed virtual host that matches the IP address
will be used.
As a consequence, the first listed virtual host is the default
virtual host. The
DocumentRoot from the main server will
never be used when an IP address matches the
NameVirtualHost 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
<VirtualHost> container and list
it first in the configuration file.
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 primary name-based virtual host).
There is a possible workaround with the
directive, albeit a slightly cumbersome one:
NameVirtualHost 220.127.116.11 <VirtualHost 18.104.22.168> ServerName www.domain.tld ServerPath /domain DocumentRoot /web/domain </VirtualHost>
What does this mean? It means that a request for any URI beginning with
"/domain" will be served from the virtual host
www.domain.tld This means that the pages can be accessed as
http://www.domain.tld/domain/ for all clients, although clients
sending a Host: header can also access it as
In order to make this work, put a link on your primary virtual host's page to http://www.domain.tld/domain/ Then, in the virtual host's pages, be sure to use either purely relative links (e.g., "file.html" or "../icons/image.gif" or links containing the prefacing /domain/ (e.g., "http://www.domain.tld/domain/misc/file.html" or "/domain/misc/file.html").
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.
See also: ServerPath configuration example