ESRI's Network Analyst extension is a powerful tool for enabling routing and network connectivity functionality within ArcGIS. The extension is commonly used for street routing and finding the best path between two points along a road network. The route can be constrained by a number of impedence factors, such as traffic or left turns, to best model the reality of road travel. Similar analyses can be run using other types of networks, such as water pipe networks or electrical networks.

To use the Network Analyst extension, the ArcGIS for Desktop advanced license is required. In ArcCatalog or ArcMap, click on the Customize menu, and select Extensions. Once the Extensions menu is open, click on the checkbox next to Turn on the Network Analyst extension.