I often get asked to differentiate the different ways to configure URLs for site collections—most often how Host Header (HH) Site Collections fit into the mix—so I thought I’d try to disambiguate this for everyone.  In the simplest explanation, there are three types of Site Collections:

·    Load-Balanced URL web application:   A single root URL that is shared amongst all contained site collections.  For example, you could have http://sharepoint, http://my, or http://teams.  There is one root site collection (matches web application URL) and additional site collections can be created at Managed Paths under this URL (http://sharepoint/sites/zach).

·    Host header web applications: Similar to a load-balanced URL web application, except the URLs all use a single host header (e.g.: http://www.foo.com).

·    Host Header Site Collection: These are site collections that each have their own unique host header. For example, http://foo.com and http://bar.com.  These sites are by far the easiest to rename—use STSADM –o RenameSite to change a HH Site Collection host header.  These site collections must still be hosted in a web application—but the Web App URL or Host Header is ignored for these sites.

While host header site collections give the most flexibility for offering multiple unique FQDNs, there are some limitations:

·    Only 1 site collection can use a unique Host Header

·    Managed Paths do no work

·    AAMs are not used as part of site lookup for HH Site Collections, so URL re-writing will not work

·    SSL Termination at the load balancer will not work  (due to lack of AAM support)

It’s important to note that Host Header Site Collections can only be created from the command line—in the STSADM command createsite, provide the Host Header for the SPSite in the URL parameter and then provide the url of the web application that will host the HH Site Collection.   The good news is that for those of you familiar with previous versions of SharePoint, there is no longer a “Host Header Mode”; HH Site Collections can be created at anytime on existing web applications.