server’s IP assignment. 
  Lease  Time:  The  length  of  time  for  the  IP  address  lease. 
Configuring a proper lease time improves the efficiency for 
the DHCP server to reclaim disused IP addresses. 
 
For example: If the lease time is set to one hour, then the DHCP 
server will reclaim disused IP addresses every hour. 
 
8.2 DHCP Client List/ Static Assignment   
The DHCP Client List section displays a DHCP dynamic client 
list, which includes host name, IP address, MAC address and lease 
time info. 
Static  Assignment:  If  you  would  like  some  devices  on  your 
network  to  always  have  fixed  IP  addresses,  you  can  use  this 
feature and manually add a static DHCP assignment entry for each 
such device. And then a registered MAC will get a correspondingly 
reserved  IP  address  while  an  unregistered  MAC  will  be  assigned 
with an unused IP address.