Q:

How does StackExchange support subdomains?

Background:
I have read an answer to the question : Which tools and technologies are used to build the Stack Exchange Network?. It is mentioned that IIS 8.0 is used as a WebServer. 
Question:
In IIS, If one wants to set up subdomains, one will have to create a new website with the subdomain. 
How has StackExchange addressed this issue as they have so many subdomains? Have they created these many websites using IIS like this:
http://meta.stackexchange.com
http://webapps.stackexchange.com
http://gis.stackexchange.com
http://mathematica.stackexchange.com
http://ux.stackexchange.com

A:

The Q&A sites are the wildcard binding in IIS (of which you can only have one), so anything hitting *:80 hits out multi-tenancy application pool. Beyond that we're looking Host header to determine which theme, database, etc. you are given on the request.

