Available with Network Analyst license.
You can accomplish some tasks that are related to the ArcGIS Network Analyst extension without actually installing and enabling the extension; however, you need to install and enable it before you can harness all of its functionality. This topic provides an overview of the functionality that is available depending on whether the ArcGIS Network Analyst extension is enabled.
ArcGIS Desktop with the ArcGIS Network Analyst extension license
All the network analysis and network dataset capabilities are available to you when the ArcGIS Network Analyst extension is enabled. Thus, you can perform any of the network analyses that the ArcGIS Network Analyst extension provides; you can also create, edit, and build network datasets. This holds true whether you have ArcGIS Desktop Basic , Desktop Standard, or Desktop Advanced installed.
ArcGIS Desktop Basic, Desktop Standard, and Desktop Advanced
Keep in mind that although Network Analyst functionality doesn't encompass editing, you may need to edit features that participate, or will participate, in a network dataset. In such a case, your ArcGIS Desktop license level (ArcGIS Desktop Basic, Desktop Standard, Desktop Advanced) determines which editing tools are available and, thus, may affect the accuracy of the results. For example, ArcGIS Desktop Standard offers functionality that ArcGIS Desktop Basic does not, such as topologies, subtype editing, and advanced feature dataset management. ArcGIS Desktop Advanced builds on the capabilities offered by ArcGIS Desktop Standard to include tools like Integrate, which creates vertices on intersecting lines. Higher ArcGIS Desktop license levels help you to more quickly and accurately model transportation networks.
ArcGIS Desktop without the ArcGIS Network Analyst extension license
The following capabilities are enabled even without an ArcGIS Network Analyst extension license:
- View properties of network datasets.
- View network dataset layers, including any associated traffic feeds, in ArcMap.
- View network analysis layers in ArcMap.
- Change properties of network analysis layers.
The only capabilities that you won't have access to are the following:
- Creating, building, and rebuilding network datasets
- Solving network analysis layers
Find Route
Even without an extension, ArcGIS Desktop provides route analysis capability through the Find Route dialog box. You can click the Find Route button 
on the ArcMap Tools toolbar to open the dialog box. Yet the Find Route dialog box doesn't give you the full range of analysis options that the ArcGIS Network Analyst extension route analysis layer provides.
ArcGIS Engine, ArcGIS Server, and the ArcGIS Network Analyst extension
Network Analyst functionality is also available as an extension to ArcGIS Engine and ArcGIS Server. A separate ArcGIS Network Analyst extension license is required for each application, since it isn't interchangeable. This means you need an ArcGIS Network Analyst extension license specifically made for ArcGIS Engine to use Network Analyst functionality in ArcGIS Engine. Similarly, you need a distinct ArcGIS Network Analyst extension license to use Network Analyst functionality in ArcGIS Server.