Joel:
Everything that Westa described about the mechanics of your http request to the server is correct. However, what he did not elaborate on is the router/firewall factor to address this. You see, what you are trying to do from what I understand, access your own server from the inside using the external address, is actually a common occurrence, I do it all the time on my own net as well as my customers'. In the past, firewalls/routers (specially when they were separate boxes) could get really confused about this and you needed to carefully tweak your DNS settings to route everything properly. Now, with "modern" turnkey routers/firewalls like the Linksys I have at home, it is done automagically. So, I am on my LAN, same segment as my server, but on my laptop, I can connect to my Web site using
www.realoutsidedomainname.com. The Linksys router just knows what to do with this traffic, yes, it will let the traffic go "out" and "come back" on the external WAN address and route the request to the server as a regular external request. The port forwarding must be setup properly on the router of course, but if you did it before, it should still work for port 80.
Now, I ran into a clients' situation where they could not do this. I needed to test the setup of what we were trying to do using the external address like they would from home but we were still in the office. What I found is that their router has a specific parameter setting to allow or disallow the internal traffic from making requests using the external interface. All I did was to allow this type of traffic in the routers admin interface and everything worked perfectly. I don't remember what brand that router is by the way, but is not a Linksys.
Regarding using an address like Pearland.Pearland.com, I do that all the time for testing also. But you have to define that address in the IIS site settings as a new Host Header name. In addition, you need to add the same address in DNN as an alias. To do this, connect to the site at the server console using localhost or modify the PortalAlias table directly.
By the way, just to test the DNS resolution part by itself, without getting DNN involved, just put a plain HTML file at the root of the DNN site, then you can use something like Pearland.Pearland.com/testfile.htm. Your browser must be able to display that page before you even attempt to deal with the DNN settings.
Hope I didn't confuse you more...
Carlos