OSPF Convergence

Regardless of which two methods of route calculation that OSPF uses, the cost of any given route path is the sum of the costs of all interfaces encountered along the path.

OSPF calculates route costs in one of two ways:

• A non-bandwidth-sensitive default value can be used for each OSPF interface.

• OSPF can automatically calculate the cost of using individual router interfaces.

At a minimum, OSPF uses bandwidth to calculate the cost of a route, using the formula (108/Bandwidth). Table 247 demonstrates some of these default calculated costs.

Table 24-7. OSPF Link Costs

Interface

OSPF Cost

100 Mbps FDDI/Ethernet

1

45 Mbps T3

2

10 Mbps Ethernet

10

1.544 Mbps T1

~64 (64.7)

56 kbps

1,768

OSPF convergence is based on the adjacency mechanism.

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