This attribute specifies the metric type in the OSPF external link state
advertisement of the routes being exported as a result of matching this
export policy.
If the attribute advertiseStatus is set to block, then the value of
extLsaMetricType is ignored. The extLsaMetricType value is not used to
select which routes to block or send, but rather the metric value
advertised for the routes.
The value useProtocolDefault indicates the metric type is automatically
chosen based on the routing protocol which the route was learned from.