Indicates the time selection mode for reallocating VMAC addresses to users.
Options:
1. macLearning(1) -indicates that the VMAC addresses are
reallocated to users after the corresponding MAC address learning entry ages.
2. dhcp(2) -indicates that the VMAC addresses are reallocated to users after
the corresponding IP addresses are released or the lease time of the IP address expires.
This leaf is optional for creating a VLAN service profile.