SharePoint 3 is bound to host headers

With the old SharePoint we were using host headers much more freely. When the site was extended, all you needed to do is add additional host headers in the Internet Information Services console.

With SharePoint 3 the story is a bit different. When you create a site with host header through SharePoint Central Administration, that site is bound to the host header you created it with. This might cause problems with intranets (for example internal domain is one and external is other). Below is one solution (that I confess, I still have to try out) that might solve this problem:

Modifying ports and host headers on SharePoint

I also use the following trick: When the site is created, I go to the IIS administration console and add the desired host headers. Usually this will redirect to the original host header. Example: site is created with www.piflar.com, I've added also host header piflar.com. So when I visit http://piflar.com it automatically redirects to www.piflar.com.

The problem might occur with intranet sites. Internal domain can be http://companyweb2 and external http://intranet.company.com:444. If you visit the second url and redirects you to companyweb2 naturally you won't be able to open the site.  

The solution can be that you add the default.aspx after the url. So if you visit http://intranet.company.com:444/default.aspx you won't get redirected and you can see the SharePoint.