This read-write field selects the routing metric for QoS Class 3 path-selection decisions, again settable independently of the other classes' metrics. An admin might reasonably select administrative-cost for class 3 if that class carries business data that is more cost-sensitive than latency-sensitive, letting the network favor the cheapest available path for that traffic. For example, setting lportAtmRouteMetricQoS3 to administrative-cost(1) means class-3 connections are routed to minimize lportTrkAdminCost across candidate trunks, prioritizing cost efficiency over squeezing out the last millisecond of delay.