Network Analysis allows you to perform analysis on Network Datasets. These analyses include finding shortest paths, drive time polygons, and closest facilities. The Network Analysis drop down menu on the Analysis tab allows you to create one of the analysis layers by choosing an analysis layer type from the drop down menu. The newly created network analysis layer is added to the table of contents.
The network analysis layers can be created using a local Network Dataset or with logistic services hosted in ArcGIS Online or portal. You can use this menu to change the default network source for creating new network analysis layers.