valid-lifetime and preferred-lifetime values of 0 seconds
kea-dhcp6:
If a client sends a DHCPRELEASE and "expired-leases-processing" settings "hold-reclaimed-time" and "flush-reclaimed-timer-wait-time" are both non-zero, the client may subsequently receive an advertise on the same address with "valid-lifetime" and "preferred-lifetime" values of 0 seconds
There are further detail in the RT ticket. RT #21806
Edited by Peter Davies