Command Center

Running several name-based web
sites on a single IP address.

Your server has a single IP address, and multiple aliases (CNAMES)
point to this machine in DNS. You want to run a web server for
www.example1.com and www.example2.org on this
machine.

The asterisks match all addresses, so the main server serves no
requests. Due to the fact that www.example1.com is first
in the configuration file, it has the highest priority and can be seen
as the default or primary server. That means
that if a request is received that does not match one of the specified
ServerName directives, it will be served by this first
VirtualHost.

The above configuration is what you will want to use in almost
all name-based virtual hosting situations. The only thing that this
configuration will not work for, in fact, is when you are serving
different content based on differing IP addresses or ports.

Name-based hosts on more than one
IP address.

The server has two IP addresses. On one (172.20.30.40), we
will serve the "main" server, server.domain.com and on the
other (172.20.30.50), we will serve two or more virtual hosts.

Any request to an address other than 172.20.30.50 will be
served from the main server. A request to 172.20.30.50 with an
unknown hostname, or no Host: header, will be served from
www.example1.com.

Serving the same content on
different IP addresses (such as an internal and external
address).

The server machine has two IP addresses (192.168.1.1
and 172.20.30.40). The machine is sitting between an
internal (intranet) network and an external (internet) network. Outside
of the network, the name server.example.com resolves to
the external address (172.20.30.40), but inside the
network, that same name resolves to the internal address
(192.168.1.1).

The server can be made to respond to internal and external requests
with the same content, with just one VirtualHost
section.

Now requests from both networks will be served from the same
VirtualHost.

Running different sites on different
ports.

You have multiple domains going to the same IP and also want to
serve multiple ports. By defining the ports in the "NameVirtualHost"
tag, you can allow this to work. If you try using <VirtualHost
name:port> without the NameVirtualHost name:port or you try to use
the Listen directive, your configuration will not work.

IP-based virtual hosting

The server has two IP addresses (172.20.30.40 and
172.20.30.50) which resolve to the names
www.example1.com and www.example2.org
respectively.

Requests for any address not specified in one of the
<VirtualHost> directives (such as
localhost, for example) will go to the main server, if
there is one.

Mixed port-based and ip-based virtual
hosts

The server machine has two IP addresses (172.20.30.40 and
172.20.30.50) which resolve to the names
www.example1.com and www.example2.org
respectively. In each case, we want to run hosts on ports 80 and
8080.

Mixed name-based and IP-based
vhosts

On some of my addresses, I want to do name-based virtual hosts, and
on others, IP-based hosts.

Using Virtual_host and
mod_proxy together

The following example allows a front-end machine to proxy a
virtual host through to a server running on another machine. In the
example, a virtual host of the same name is configured on a machine
at 192.168.111.2. The ProxyPreserveHost On directive is
used so that the desired hostname is passed through, in case we are
proxying multiple hostnames to a single machine.

Using _default_
vhosts

_default_ vhosts
for all ports

Catching every request to any unspecified IP address and
port, i.e., an address/port combination that is not used for
any other virtual host.

Using such a default vhost with a wildcard port effectively prevents
any request going to the main server.

A default vhost never serves a request that was sent to an
address/port that is used for name-based vhosts. If the request
contained an unknown or no Host: header it is always
served from the primary name-based vhost (the vhost for that
address/port appearing first in the configuration file).

You can use AliasMatch or
RewriteRule to rewrite any
request to a single information page (or script).

_default_ vhosts
for different ports

Same as setup 1, but the server listens on several ports and we want
to use a second _default_ vhost for port 80.

The default vhost for port 80 (which must appear before any
default vhost with a wildcard port) catches all requests that were sent
to an unspecified IP address. The main server is never used to serve a
request.

_default_ vhosts
for one port

We want to have a default vhost for port 80, but no other default
vhosts.

A request to an unspecified address on port 80 is served from the
default vhost any other request to an unspecified address and port is
served from the main server.

Migrating a name-based vhost to an
IP-based vhost

The name-based vhost with the hostname
www.example2.org (from our name-based example, setup 2) should get its own IP
address. To avoid problems with name servers or proxies who cached the
old IP address for the name-based vhost we want to provide both
variants during a migration phase.

The solution is easy, because we can simply add the new IP address
(172.20.30.50) to the VirtualHost
directive.

The vhost can now be accessed through the new address (as an
IP-based vhost) and through the old address (as a name-based
vhost).

Using the ServerPath
directive

We have a server with two name-based vhosts. In order to match the
correct virtual host a client must send the correct Host:
header. Old HTTP/1.0 clients do not send such a header and Apache has
no clue what vhost the client tried to reach (and serves the request
from the primary vhost). To provide as much backward compatibility as
possible we create a primary vhost which returns a single page
containing links with an URL prefix to the name-based virtual
hosts.

Due to the ServerPath
directive a request to the URL
http://www.sub1.domain.tld/sub1/ is always served
from the sub1-vhost.
A request to the URL
http://www.sub1.domain.tld/ is only
served from the sub1-vhost if the client sent a correct
Host: header. If no Host: header is sent the
client gets the information page from the primary host.

Please note that there is one oddity: A request to
http://www.sub2.domain.tld/sub1/ is also served from the
sub1-vhost if the client sent no Host: header.

The RewriteRule directives
are used to make sure that a client which sent a correct
Host: header can use both URL variants, i.e.,
with or without URL prefix.