This object sets the expense metric value to announce this Level 2 summary address with, where zero indicates the metric isn't supported. Administrators use this optional metric to reflect the monetary or bandwidth cost of a path when that consideration matters more than simple hop count. For example, an engineer sets a nonzero csIsisL2SummAddrExpenseMetric for a summary address reached only via an expensive metered WAN circuit, discouraging its use except when the lower-cost primary path is unavailable.