Multiplex Nether Portal

First, you need to build a vanilla nether portal. If you are done you have to place a sign below the portal with the word portal in the first line. Make sure that the obsidian above the sign has air above it. Now the sign only needs a redstone signal to open a navigation GUI. In the GUI you can select your target destination and unlock other dimensions like the End, Twilight Forest etc.

The video below will show you how to setup the portal for our 1.7 servers:

The video below will show you how to setup the portal for our 1.10 servers: