I have a couple of different offices that use Linux boxes as combined routers and transparent proxies. All of them are working fine, apart from one which is having a weird issue when attempting to view a web page via IP. Using this website as an example, if I surf to;
It works fine.
However, if I surf to;
It will immediately drop me to a standard 'page cannot be displayed' message.
If I bypass the transparent proxy, say by trying to load the page on the router itself, it works fine, so I don't believe it is an ISP issue.
My other locations using seemingly identically configured proxies can access pages by IP fine.