Please telnet to the router and use the command "srv dhcp leasetime xxx " to set the lease time. Then type command 'sys reboot' to reboot the router for activating the setting.Refer to the following figure:
telnet
Account:admin Password: ******* User login successful, expired time is "Unlimited". Type ? for command help > srv dhcp leasetime ? % srv dhcp leasetime <Lease Time <sec.>> % Now: 259200 > srv dhcp leasetime 86400 > > sys reboot
Account:admin
Password: *******
User login successful, expired time is "Unlimited".
Type ? for command help
> srv dhcp leasetime ? % srv dhcp leasetime <Lease Time <sec.>> % Now: 259200
> srv dhcp leasetime 86400 > > sys reboot