Greg - SiteOrigin

I built this plugin to help ease the transition during a DNS changeover, but you can use it any way you please. It turns your WordPress installation into a very simple proxy server. It fetches content from another URL, caches it and displays it. Requests are cached for 24 hours.
Install the plugin, then head over to Settings > Simple Proxy in your WordPress admin. Enter the URL you want to proxy to and when you’re ready to go, also check the enabled checkbox.
You need to have <a href="https://codex.wordpress.org/Using_Permalinks#Choosing_your_permalink_structure" rel="nofollow ugc">pretty permalinks</a> enabled.
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Simple Proxy

Turns your WordPress installation into a simple caching proxy.

Samuel Parsons

If you’re running WordPress behind a proxy, chances are that the IP address of the user browsing your site won’t show up, instead WordPress will see the IP address of your proxy server. Proxy Real IP sets this straight by looking at the HTTP headers that the proxy sends.
Proxy Real IP looks in the following HTTP headers: 
X-FORWARDED-FOR, X-FORWARDED, FORWARDED-FOR, FORWARDED, X-REAL-IP
Proxy Real IP sets the user’s IP address to the first HTTP header defined that matches a simple regular expression of an IP address (123.123.123.123).
Proxy Real IP also sets the $_SERVER[‘HTTPS’] variable correctly when running behind a proxy so that WordPress can determine whether or not the proxy connection is over HTTPS. It looks to the HTTP_X_FORWARDED_PROTO PHP server variable to determine this.

Proxy Real IP

Proxy Real IP is a simple plugin that sets user's IP addresses correctly when running WordPress behind a load balancer or other proxy.

Simple Proxy vs Proxy Real IP