This read-create object sets the default routing metric IS-IS advertises for reaching the destination configured in the corresponding csIsisIPRADest entry over this circuit. It directly influences path selection in the network, since other IS-IS routers will prefer lower-metric paths to reach that prefix. An administrator wanting traffic to prefer a primary WAN circuit over a backup would set a lower csIsisIPRADefMetric value on the primary circuit's reachable-address entry than on the backup's.