Article Link: http://help.truecommerce.com/en/articles/4389074-nexternal-display-your-domain-name-in-the-url-of-your-store-pages
To display your own domain in the URL bar of your Nexternal online store, create a new DNS CNAME record. You will need to do this through the company that hosts your DNS (typically your web hosting company).
Point this CNAME record to "www.nexternal.com" (do not forget the www part!). Use a new sub-domain as opposed to an existing one. For example, use store.YOURDOMAIN.com or shop.YOURDOMAIN.com rather than www.YOURDOMAIN.com.
Once the CNAME record is created, log in to your Nexternal Order Management System. Navigate to Settings/Site Options/ Domain Alias and specify the domain alias (store.YOURDOMAIN.com or shop.YOURDOMAIN.com). This will replace "nexternal" in the URL with your own domain, on every page before log in and check out.
If you would like your domain alias to show up in your B2B store, or to persist after login or checkout in your B2C store, you also need to request a "Secure Domain Alias" (Settings/Site Options/Secure Domain Alias), and after it is installed, select "Always Secure". Annual fee applies.
We recommend using a CNAME record whenever possible, but if your DNS host is requiring an IP address, then you must use an A Record (vs a CNAME) and you can point it to the IP Address 184.108.40.206