Multisite Domain Mapping and Configuration

A multisite can have either subdirectory or a subdomain structure.

If a multisite installation uses subdirectories, each of the subsites can be mapped with its own domain. Remember to define this domain in the Siteurl and Home fields in the individual subsite settings.

If the subsites already have content and links, the address structure must be updated in the sites' database with search-replace command. You can use Seravo Plugin's features to run this command.

If you are using a subdomain-based installation and mapping custom domains to sub-sites, you must add the following line to your wp-config.php file to ensure logins work correctly without errors:

If your multisite uses a subdomain structure and has Mercator installed, the plugin can be used to map sub-sites to separate domains. Once Mercator is installed, a new field called Aliases will appear in the All Sites menu.

In the picture below, in the leftmost column, URL must always show the actual subdomains however, in order for the site cookies to function properly. In a subdomain multisite, accessing the subsite admin panel requires re-login.

Also the subsite's Site Address (URL) setting must always show the subdomain.

The separate domain must be defined as an Alias, and must of course be marked as active. Do note that while several aliases can be added, it is recommeneded to have only one active alias. If the intention is to direct several additional domains to a multisite subsite, it is recommended to use an nginx redirect instead.

Once a domain has been defined as an Alias for a subsite, it must also be configured as the subsite's Siteurl and Home (see the Settings-tab).

Publishing a multisite differs from the publishing of a normal site in certain ways. Unlike the standard process, it is advisable to change the addresses in the multisite database manually in advance using search-replace. In addition to this, the address must also be changed in the wp-config.php file, which is located on the server at the path /data/wordpress/htdocs/.

This file contains a number of multisite-related definitions, one of which is the site's primary address. The line you want to edit is the following:

define( 'DOMAIN_CURRENT_SITE', 'example.fi-c.seravo.com' );

Change the development address to the final primary domain for the site and save the changes. After these changes, the site will no longer be accessible via the browser until the primary domain has been pointed to our server and the DNS has had time to update. Despite this, it is still recommended to point the DNS after making the changes, as this allows our publishing automation to automatically generate the certificate and keeps the downtime associated with publication as small as possible.

If the domain starts point to our server before the addresses are changed in the database and the wp-config.php file, it will lead to the site being non-functional until both changes have been made.

If you encounter issues after mapping domains, here are the solutions to the most common errors.

This is usually caused by a configuration mismatch. Ensure you have added the COOKIE_DOMAIN definition to your wp-config.php file as instructed above:

This typically occurs if there is a conflict between internal site settings and server-side redirections. Double-check that both the Site URL and Home URL in the network admin settings exactly match your primary domain.

If the domain redirects to the WordPress signup page, the network does not recognize it.