Iis – No response from IIS

TCP    [::1]:52404            mgibson-dev:9001       SYN_SENT

This line seems to imply that you've tried to initiate an ipv6 connection to 'mgibson-dev' on port 9001. The SYN_SENT bit means that you've fired off a TCP SYN packet but not heard a response back.

If you're not listening on an ipv6 localhost address on TCP 9001, my initial guess would be that you have a firewall somewhere that's dropping the return packet somewhere. Normally, if the port's closed, you would expect a RST packet back, and then it would know the port isn't open and would try the ipv4 address. Because the RST packet's not coming through, it just hangs waiting for a response and eventually will time out.

In short, check your firewall to allow all inbound from localhost on both ipv4 and ipv6.

Problem solved. I finally decided to compare the module list side-by-side and there actually was one missing. It turns out that there are two Windows Authentication modules:

On the server, the managed WindowsAuthentication module was there, but not the native WindowsAuthenticationModule highlighted above. Why it was configured that way is anyone's guess, but apparently if the native module is not loaded, the managed module will cheerfully load and silently fail.

So for any future readers who encounter this problem, make sure you have both modules loaded, because IIS will not warn you if one of them is missing.