DXS-3326GSR Gigabit Layer 3 Switch
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.
Figure 7- 15. Constructing a Shortest Path Tree
Router A
Router B
Router C
Router D
128.213.0.0
192.213.11.0
222.211.10.0
0
10
10
5
5
10
10
Figure 7- 16. Constructing a Shortest Path Tree
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:
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