This attribute specifies the metric to be used on the routes being
exported as a result of matching this export policy.
If the attribute advertiseStatus is set to block, then the value of
exportMetric is ignored. The exportMetric value is not used to select
which routes to block or send, but rather the metric value advertised for
the routes.
A value of 0 indicates that the metric associated with the route in the
forwarding table is used.