How do I switch monitor focus with the keyboard? I have 2 monitors connected to my Mac. 
Each monitor has multiple spaces setup, for example - monitor 1 has Desktop 1, 2 &amp; 3 and monitor 2 has Desktop 4 &amp; 5.

ctrl+← and ctrl+→ only move between spaces on the currently focused monitor.

However, I can't find how to switch monitor focus using the keyboard.

If focus is on monitor 1, I need to point and click my mouse on monitor 2 and only then can I switch spaces on monitor 2.

Even if I switch to an application open on monitor 2 using ctrl+tab, the monitor focus and space switching still occurs on monitor 1.

Using Yosemite.
fwiw, I think this question has already been asked and answered...

Keyboard shorcut to switch focus between multiple displays on OS X Mavericks