OSPF External Metrics Overview
When OSPF exports route information from external ASs, it includes a cost, or external metric, in the route. There are two types of external metrics: Type 1 and Type 2. Type 1 external metrics are equivalent to the link-state metric; that is, the cost of the route used in the internal AS. Type 2 external metrics are greater than the cost of any path internal to the AS.
