WordPress can be installed very easily in many different server configurations. However, when enabling WordPress Multi-Site Network there are some requirements you must follow.

Below, I have copied the server requirements from The WordPress Codex. You must make sure you are able to run Multi-Site successfully before installing the Multi-Site Enabler Plugin. Most servers support one form of the Multi-Site installation.

Please read the documentation below before continuing.

Before You Begin

Server Requirements

Since this feature requires extra server setup and more technical ability, please check with your webhost and ask if they support the use of this feature.

You are given the choice between sub-domains or sub-directories . This means each additional site in your network will be created as a new virtual subdomain or subdirectory.

• Sub-domains — like site1.example.com and site2.example.com
• Sub-directories — like example.com/site1 and example.com/site2

Sub-directory sites

It works with the use of the mod_rewrite feature on the server having the ability to read the .htaccess file, which will create the link structure.

If you are using pretty permalinks in your blog already, then subdirectory sites will work as well.

Sub-domain sites

It works using wildcard subdomains. You must have this enabled in Apache, and you must also add a wildcard subdomain to your DNS records. (See below how to set up.)

Some hosts have already set up the wildcard on the server side, which means all you need to add is the DNS record.

Some shared webhosts may not support this, so you may need to check your webhost before enabling this feature.

WordPress Settings Requirements

• Giving WordPress its own directory will not work in WordPress 3.0 with multisite enabled. It interferes with the member blog lookup.
• You cannot create a network in the following cases:
  • “WordPress address (URL)” is different from “Site address (URL)”.
  • “WordPress address (URL)” is used port number other than ‘:80′, ‘:443′.
• You cannot choose Sub-domain Install in the following cases:
  • WordPress install is in a directory (not in document root).
  • “WordPress address (URL)” is localhost.
  • “WordPress address (URL)” is IP address such as 127.0.0.1.

Setting Wildcard Subdomains

Sub-domain sites work with the use of wildcard subdomains. This is a two-step process:

1. Apache must be configured to accept wildcards.
   1. Open up the httpd.conf file or the include file containing the VHOST entry for your web account.
   2. Add this line:

      ServerAlias *.example.com

2. In the DNS records on your server, add a wildcard subdomain that points to the main installation. It should look like:

   A *.example.com

External links:

• Wildcard DNS record (Wikipedia)
• Apache Virtual Host (Apache HTTP Server documentation)