When you create a portal alias in DotNetNuke, when you browse to the new URL that you gave it, you get a page not found error.  

When you create a portal alias, that allows DotNetNuke to respond to your hosting requests, however, it does not let the DNS servers or IIS webserver get the requests so that it can pass them to your DotNetNuke website.  

In order to make parent portals work, you need to add a domain alias (also known as a host header) to your DNN website.  Here's how you do this:

1)  Log into your control panel
2)  Click the System tab.
3)  Scroll down and click on your domain
4)  Click on the "Domain Aliases" button.
5)  Add a new domain alias.  Make sure to select all 3 options when creating the alias.
6)  Make sure that you have set the alias's name servers to be NSA.PowerDNN.com and NSB.PowerDNN.com

Please remember that after you create the domain alias, it will take about 30-60 minutes for it to sync through the system so please be patient while the changes take place.