This is another alternate routing metric slot for the route, with its meaning defined by the protocol named in aniDevRouteProto and set to -1 when the protocol doesn't populate it. Admins would consult it only when working with a routing protocol that exposes a third distinct cost dimension for path selection. For example, a route from a protocol with multiple metric fields might use aniDevRouteMetric3 to hold a tie-breaking value, while most simpler protocols leave it at -1.