WordPress support documents state that you are required to add a wildcard entry for Apache in the httpd.conf as well as in your DNS zone to use WordPress MultiSite on subdomains. On a cPanel server this process is extremely simple as you can accomplish this in only a few simple steps.
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- Log into your cPanel account.
 - Click on "Subdomains" under the "Domains" group.
 - Enter a single "*" into the subdomain line and choose which domain you wish to add the wildcard to in the drop-down box. (Demonstration Image)
 - Enter the directory where WordPress Multisite is installed into "Document Root".
 - Click "Create"
 
 
You have now added a wildcard subdomain entry to your DNS zone with us as well as the Apache configuration file (httpd.conf).