Apache HTTP Server Version 2.0
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This document describes when and how to use name-based virtual hosts.
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:
Related Modules | Related Directives |
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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
. 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 the 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.
<VirtualHost>
block for the existing host.
The ServerName
and
DocumentRoot
included in this virtual
host should be the same as the global ServerName
and 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 httpd.conf
:
NameVirtualHost *
<VirtualHost *>
ServerName www.domain.tld
ServerAlias domain.tld *.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 both the NameVirtualHost
and <VirtualHost>
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.
Many servers want to be accessible by more than one name. This is
possible with the ServerAlias
directive, placed inside the <VirtualHost>
section. For
example in the first <VirtualHost>
block above, the ServerAlias
directive indicates that the
listed names are other names which people can use to see that same
web site:
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 ServerName
or 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 overridden 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
ServerName
or
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).
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 Host
header as
required for name-based virtual hosts.
There is a possible workaround with the ServerPath
directive, albeit a slightly cumbersome one:
Example configuration:
NameVirtualHost 111.22.33.44
<VirtualHost 111.22.33.44>
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 http://www.domain.tld/
.
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.
Available Languages: en