How to add a wildcard DNS record

Any subdomain that uses wildcard DNS will redirect to your main domain.
For instance, when set, mydomain.com will be the default website for anyone inputting subtest.mydomain.com or subtest123.mydomain.com.
When ww is typed incorrectly, it can also be used to reroute searches like ww.mydomain.com to www.mydomain.com.
One of three methods can be used to set up a WildCard subdomain:

1. Setting it from cPanel
2. Setting it from WHM
3. Setting it from httpd.conf

1. Setting it from cPanel
a. Log into your cPanel
b. Go to Subdomains
c. Add subdomain * in the box next to the field ‘Subdomain’ of your primary domain. Make sure that the Document Root is set to public_html folder.
While adding Wildcard subdomain to your Addon domain, you just need to be sure to set the Document Root to that of the Addon Domain and not the primary domain.

2. Setting it from WHM

If you have access to WHM, then you need to
a. Go to Edit DNS Zone
b. Select the required domain
c. Under Add New Entries Below this Line insert as below

NOTE: Please replace 20.x.xx.xx with the actual IP of the account.

3. Setting it from httpd.conf
 In order to use this method, you need root access to the server.
a. Login as root
b. Edit httpd.conf  (commonly located at /etc/httpd/conf) with your favorite text editor such as Vim or Nano and go to the VirtualHost entry of the domain/website.

<VirtualHost 20.x.xx.xxx:80>
ServerName mydomain.com
ServerAlias www.mydomain.com
DocumentRoot /home/mydomain/public_html
ServerAdmin webmaster@mydomain.com
UseCanonicalName Off
CustomLog /usr/local/apache/domlogs/mydomain.com combined
CustomLog /usr/local/apache/domlogs/mydomain.com-bytes_log “%{%s}t %I .\n%{%s}t %O .”

c. The line ServerAlias www.mydomain.com is of your interest. Simply replace www with * which should look like ServerAlias *.mydomain.com

That’s it !