The value of vRtrIfDhcp6ClStateLeasePrefLftm indicates the UTC date when the preferred lifetime of the private IP address (i.e., vRtrIfDhcp6ClStateCiAddr) will expire. In the preferred state, vRtrIfDhcp6ClStateCiAddr can be used without any restriction. Once the lifetime expires, vRtrIfDhcp6ClStateCiAddr is still valid, but needs to be renewed or rebound.