How-to set the Lease Time for DHCP granted IP address | FortiOS

Environment
  • FortiOS 5.2.x

Content
Once day got could not get DHCP IP address but WiFi connection OK. Checked the IP address granted from DHCP service full. Many not released although not online over days.

Best to set the Lease Time shorter. However, could not find it on Web-UI. Finally, identified that required us to set it via CLI:

# config system dhcp server
# show
[...]

edit 2
   set dns-service default
   set default-gateway 192.168.0.1
   set netmask 255.255.255.0
   set interface "public-wifi"
   config ip-range
   edit 1
      set start-ip 192.168.0.100
      set end-ip 192.168.0.150
   next
end
next

[...]

# edit 2
# set lease-time 28800

#@note 300 ~ 8640000 seconds; 0 for unlimited lease time


Update