080122 : Network Analyst extension is not enabled or not installed.

Description

Network Analyst must be installed, licensed and activated to perform this function.

Solution

From with ArcMap select the Tools drop down menu and select Extensions and verify that the Network Analyst Extension is enabled. If Network Analyst is available in the list of extensions but is greyed out then the license has not been activated. If Network Analyst does not appear in the list of extensions then you it must be installed. For Custom installation options consult your ArcGIS installation document.