Read this page before you use Realtime Global Illumination (GI) on models which use the LOD (level of detail) feature.
When you use Unity’s LOD system in a Scene with baked lighting and Realtime GI, the system lights the most detailed model out of the LOD Group as if it is a regular static model. It uses lightmaps for direct and indirect lighting, and separate lightmaps for Realtime GI.
To allow the baking system to produce real-time or baked lightmaps, select the GameObject you want to affect, view its Renderer component in the Inspector window, and check that Lightmap Static is enabled.
Whenever you use Realtime GI, the Renderer enables the Light Probes option for the lower LODs, even if you enable Lightmap Static.