I created a streets layer with field FE (from elevation) and TE (to elevation). Please check the attachment for details.
When I set the fields to 0, the network could not be solved. And there is an Error: The source is not valid for the network.
However, when the FE and TE are set to NULL, the route is solved.
Is there any difference between the elevation 0 and NULL?
The stops are same location and the software is ArcMap 10.6 with network extension.