I came across the second part of Troy Starr's Trilogy on Alternate Access Mappings in SharePoint 2007.

It's a great series from an Administrators perpective on what they are and why you need them.

I recently 'stumbled' upon them when writing some code that accessed a site based on the URL. When I passed the internal name to the web service everything worked fine, by FQDN, IP Address, or externally accessible URL did not work (note I didn't realise that at THAT stage neither would all of the external links - see Troy's post). Once I added alternate access mappings for all the possible ways people could pass a URL to the site to SharePoint all was well.

Whatever you use as the URL when setting up your new server (and therefore becomes the URL you see when choosing application pools in central admin) is the only URL that will work 100% unless you create AAM's!!

What I think often happens is people set up a server and answer all the configuration prompts with the internal port 80 details. Then, when they come to go into production, realise that they need another port, or the server to be accessible via SSL, or FQDN and forget that AAM's need to be configured - and it's not until you try to do...

SPSite mysite=new SPSite("http://...");

 ... where the URL is not mapped that you notice it's broken. Or someone reports that some links don't work...

Great post Troy - awaiting Part 3 with antici...........pation.