Name-based virtual hosting is a fairly simple technique. You need to configure your DNS server to map each hostname to the correct IP address first, then configure the Apache HTTP Server to recognise the different hostnames.

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. Normally any and all IP addresses on the server should be used, so, 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: there are two additional directives used to restrict or specify which addresses and ports Apache listens to:

The next step is to create a <VirtualHost> block for each different host you would like to serve. The argument to the <VirtualHost> directive should be the same as the argument to the NameVirtualHost directive (i.e., 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.

Suppose that both www.domain.tld and www.otherdomain.tld point to the IP address 111.22.33.44. You then simply add the following to httpd.conf:

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>
       

In the simplest case, the IP address 111.22.44.33 can be replaced by * to match all IP addresses for your server. Many servers want to be accessible by more than one name. This is possible with the ServerAlias directive placed inside the <VirtualHost> section, if, for example, you add the following 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.

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. 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 requesting 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, it then 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.

Despite the advantages of name-based virtual hosting, there are some reasons why you might consider using IP-based virtual hosting instead:

As the term IP-based indicates, the server must have a different IP address for each IP-based virtual host. This can be achieved by equipping the machine with several physical network connections or by use of virtual interfaces, which are supported by most modern operating systems (see system documentation for details on IP aliasing and the ifconfig command).

There are two ways of configuring Apache to support multiple hosts.

Use multiple daemons when:

Use a single daemon when:

Listen 123.45.67.89:80
        

<VirtualHost www.smallco.com>
    ServerAdmin webmaster@mail.smallco.com
    DocumentRoot /groups/smallco/www
    ServerName www.smallco.com
    ErrorLog /groups/smallco/logs/error_log
    TransferLog /groups/smallco/logs/access_log
</VirtualHost>

<VirtualHost www.baygroup.org>
    ServerAdmin webmaster@mail.baygroup.org
    DocumentRoot /groups/baygroup/www
    ServerName www.baygroup.org
    ErrorLog /groups/baygroup/logs/error_log
    TransferLog /groups/baygroup/logs/access_log
</VirtualHost>