You may come across an issue where your modules cannot connect to the core server with or without going through a proxy server.  You will also find you cannot browse to the core URL with Internet Explorer, however you can browse to other websites with Internet Explorer and you will also be able to browse the core URL with other browsers excluding Internet Explorer.
You will get a DNS problem: “internet explorer cannot display the webpage”
You need to ensure you have TLS 1.1 and 1.2 enabled in the Advanced Settings of Internet Explorer Options.

It may be that you do not have options for TLS 1.1 or 1.2  This will most likely be because you are running a version of Internet Explorer that is pre-version 8 or a Windows version that is pre-Windows 2008 or Windows 7.
If this is the case there is a Microsoft Security Bulleting explaining why this is and with a fix.

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