In most cases, when you perform these kinds of analyses, you will want to take into account the resistance to travel along certain line segments, such as road speed limits, as well as physical limitations, such as pipe width. For example, the shortest distance by road between two cities may not always have the fastest journey time. There may be a freeway, which takes a longer route, but which has a much higher speed limit. (These are the kind of calculations that are made when you get driving directions from a web-based mapping service.) Another example would be the resistance to crossing a particular point, such as a valve in a water network. In AutoCAD Map 3D, you can specify link resistance and node resistance across your entire network using expressions and object-data tables.
When you open a map that has a topology defined in it, the topology is not loaded. Before you can use it, you must load it. This step also audits the topology to make sure that it is correct and complete.
There is a lot of functionality that you can use when performing a network analysis, particularly to help you specify resistance factors. However, the following demonstration keeps things simple and shows how to find the shortest path between two points in the network, without calculating any resistance. The other kinds of analysis: Best Route and Flood Trace are very similar. (If you want to learn more about the different kinds of network analysis, there is a detailed description in the AutoCAD Map 3D Help.)