While calculating shortest path, first we assume graph presentation of network at every node then we use Djikstra's algorithm to calculate shortest path from every node to other one. Then extract next hop information from giving path information and add next hop information into routing tables.

WEIGHTED GRAPH

Djikstra's algorithm will add weights on edges in graph. The shortest path is then the path with minimum total weight. It could be noticed that the shortest path is not necessarily with fewest edges. For example as given in the figure below:

The minimum path in the diagram from node 2 to node 6 is 2 to 3 and 3 to 6 as this way has the minimum weight so it is the shortest path.

DISTANCE MATRICS

Weights on graph nodes denote cost of traversing edge. This cost can be in time, hop or dollars counting (weight == 1). The resulting shortest path can not have fewest hops.