Well, in my case I set up Unraid for a small business as their storage solution, since they needed something, which has some pro features, but still is easily manageable by a not that experienced guy which is working for them. However I setup a new structure which was different from their old setup. But some devices are configured and managed by an external company to use an specific IP for their network share, which was not possible (or wished) to reconfigured or changed, so I needed to add a second IP. All that I was told after I was done with my original setups, so the easiest way was to add the additional IP.
But I really wondered that it was not possible through Unraid itself, since it is a really common feature, you find it in any PC or Server with WebGUI.
BTW what's your "MB"?