OSPF: type 1 dan type 2

When OSPF exports route information from external autonomous systems (ASs), it includes a cost, or external metric, in the route. OSPF supports two types of external metrics: Type 1 and Type 2. The difference between the two metrics is how OSPF calculates the cost of the route.

• Type 1 external metrics are equivalent to the link-state metric, where the cost is equal to the sum of the internal costs plus the external cost. This means that Type 1 external metrics include the external cost to the destination as well as the cost (metric) to reach the AS boundary router.
• Type 2 external metrics are greater than the cost of any path internal to the AS. Type 2 external metrics use only the external cost to the destination and ignore the cost (metric) to reach the AS boundary router.

By default, OSPF uses the Type 2 external metric.

Both Type 1 and Type 2 external metrics can be present in the AS at the same time. In that event, Type 1 external metrics always takes the precedence.

Type 1 external paths are always preferred over Type 2 external paths. When all paths are Type 2 external paths, the paths with the smallest advertised Type 2 metric are always preferred.

Pranala Menarik

• OSPF