D-Link xStack DGS-3600 User Manual page 145

Shortest Path Tree
To build Router A's shortest path tree for the network diagramed below, Router A is put at the root of the tree and the smallest
cost link to each destination network is calculated.
The diagram above shows the network from the viewpoint of Router A. Router A can reach 192.213.11.0 through Router B with a
cost of 10 + 5 = 15. Router A can reach 222.211.10.0 through Router C with a cost of 10 + 10 = 20. Router A can also reach
222.211.10.0 through Router B and Router D with a cost of 10 + 5 + 10 = 25, but the cost is higher than the route through Router
C. This higher-cost route will not be included in the Router A's shortest path tree. The resulting tree will look like this:
xStack DGS-3600 Series Layer 3 Gigabit Ethernet Managed Switch
Figure 8- 24. Constructing a Shortest Path Tree
128.213.0.0
5
192.213.11.0
Figure 8- 25. Constructing a Shortest Path Tree
Router A
0
10
10
Router B
Router C
5
Router D
10
222.211.10.0
129
10