One way was valid on the Intranet that was given is to go configure you HOST file on the machine that allows you to apply a IP to an URL such as
formatting link
to 192.168.1.105 as an example. The O/S looks in the HOST file first for URL to IP resolution before it goes out to the network to obtain the information from a DNS server,which in your case was being equated the WAN IP from your ISP that the WAN on the router is using because it was hitting the ISP's DNS servers on the URL lookup.
Duane :)