
Customizing OSPF Services
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Specifying the Metric Cost
For OSPF, the best path is the one that offers the least-cost metric.
You must configure cost metrics if you want to specify a preferred path. Allow the
preferred path to retain the default cost metric value of 1, and then assign
higher-cost metric values to the less-preferred paths.
Figure 6-4
illustrates the benefit of using configurable cost metrics. Assigning the
56 Kb line a cost metric value of 10 forces OSPF to choose the faster T1 line path
as the best path, despite the extra hop, when transmitting a packet from host A to
host B.
Figure 6-4. Example of Using Configurable Cost Metrics
Router 1
Router 2
Router 3
56 Kb
Assigned cost
metric = 10
T1
1.544 Mb
Assigned cost
metric = 1
T1
1.544 Mb
Assigned cost
metric = 1
Host
B
Host
A
IP0018A
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