Getting “localhost.” to work with IIS7

I’m not 100% sure why, but with IIS7, I am unable to get connect to my local IIS instance using Fiddler’s magic “localhost.” hostname.  Normally this hostname allows localhost traffic to be monitored within Fiddler. Out of the box, IIS7 was returning me the following error on requests to “localhost.”:

Bad Request - Invalid Hostname

Trying to add a secondary binding with “localhost.” explicitly set as the host yeilds another error, this time from the IIS Management Console:

Value does not fall within the expect range.

I found that editing Fiddler’s CustomRules.js provides a quick workaround while still allowing you to use the exact “localhost.” name.  Simply add the following line to the “onBeforeRequest” function:

if (oSession.host.ToUpper() == “LOCALHOST.”) { oSession.host = “localhost”; }

This fix of course only works when Fiddler is running, so please comment if you know of a workaround within IIS7.  (Alternatively, please comment if you have no issue in IIS7 — that my box simply has a case of the Vistas.)