I have three Windows hosts on the same private LAN, each hosting an IIS default website. One host is running Windows 7 Pro, while the other two are running Windows 8.1 Update Version 6.3 (Build 9600).

Other computers on the local subnet can open the default website on each of the 3 hosts by entering each host's private IP address in a browser.

However, when I Port Forward port 80 on a gateway router in turn to each of the 3 hosts private IP address, then enter the public IP of the gateway router into a browser on a computer outside of the private network, only the Windows 7 host displays its default website. The two Windows 8.1 Update hosts report "This webpage is not available. Details: The host took too long to respond." Additionally, no record of the HTTP request appears in "C:\inetpub\logs\LogFiles\W3SVC1\u\_exYYMMDD.log" on the host.

All three hosts have their Windows Firewall Inbound Rule "World Wide Web Services (HTTP Traffic-In)" set to Profile: All, Enabled: Yes, Action: Allow, Override: No, Program: System, Local Address: Any, Remote Address: Any, Protocol: TCP, Local Port: 80, Remote Port: Any, Authorized Users: Any, Authorized Computers: Any, Authorized Local Principles: Any, Local User Owner: Any, Application Package: Any. 

This problem began after I installed the mid-February Windows Update. Any help diagnosing & fixing the problem is greatly appreciated.