Certain DHCP Server parameters cannot be changed from their default settings via the LAN-Cell's Web GUI interface.  However, they can be modified from the LAN-Cell's Command Line Interface (CLI).

For example, to change the DHCP Lease Time for IP addresses assigned to LAN devices, follow these steps:

1. Make a Telnet or SSH connection to the LAN-Cell (or use the Blue Serial Console cable).
   
   
2. Enter your administrator password (same as the Web GUI password).
   
   
3. Select Menu Option #24, then Menu Option #8 to reach the Command Line Interface.
   
   
4. Enter the following command (case sensitive) and press Enter:
   ip dhcp enif0 server leasetime NNNNNN
   
   where:
   LAN = enif0
   DMZ = enif2
   WLAN - enif4
   NNNNNN = DHCP lease time in seconds (default value is 259200 or 72 hours)
   
   
5. You can confirm the new lease time value by entering the command:
   ip dhcp enif0 status
   The new value will remain in effect until the LAN-Cell is reset to factory defaults.
   
   
6. Type
   sys quit
   to exit the command interface.
   

Several other DHCP parameters can be set via the CLI including:
probecount, dnsserver, gateway, hostname, leasetime, netmask, pool, renewaltime, rebindtime

See the CLI command
ip dhcp enif0 server ?
for more details.