In Simple DNS Plus, create an A-record for the domain name without the 'www' prefix pointing to the IP address of the web-server, and create a CNAME-record for the domain name with the 'www' prefix pointing to the domain name without the prefix:
If your web-server is hosting multiple websites on the same IP address, you also need to set up both versions of the domain name in the website configuration.
The following illustrates how this is done in IIS (Microsoft's Internet Information Services) and in Apache (see further down).
In the IIS Manager select the website and select the properties function:
In the "website properties dialog" click the "Advanced" button next to the IP address field:
Add an identity entry for each version of the domain name (with and without the 'www' prefix):
In Apache, you need to put one version of the domain name in the "ServerName" setting and the other in the "ServerAlias" setting in the configuration file:
<VirtualHost *> ServerName simpledns.plus ServerAlias www.simpledns.plus # ... </VirtualHost>