|Open CMD (command prompt) and type in:|
netstat -anp tcp
Search for ip_address:80
If you get only the internal ip address, listening to port 80, there is an assignment made in the webserver configuration.
Click Start / Run and start the inetmgr.
In inetmgr, check whether only the internal IP address is assigned to the webserver.
If so, switch it to not assigned, so that the webserver acts on all network cards in the server.