Support Forum
The Forums are a place to find answers on a range of Fortinet products from peers and product experts.
New Contributor

Fortigate DHCP problems

Hi all.


Seems like my fortigate having problems with DHCP services. so this problems was started about 3-4 months before. Every morning when I connected my laptop to this network via lan cable/or via wifi. The first ip address that fortigate distribute to my laptop is wrong (it always appeared like subnet mask always be and no default gateway and this problems still occur when I connected other devices to this network like PC, or mobile phone.) When this problems occur. my current solution is clear dhcp lease-list and reestart dhcp service on internal interface. after restart dhcp service everything seems okay. Fortigate distribute correct ip (with correct default gateway) to all client that connect to it. but on the next day this problems still occured. and repeat like this on every morning.


When I tried to find a solutions on the webboard. I found something interesting like "your network might have loopback?"after I checked up my network I didn't found any lan cable that cause the loopback. my next solution is set schedule restart on my fortigate every 7 am and hope fortigate restarts dhcp services too. but seems like it didn't help much because this problems still occur.


Does anyone have any ideas about solution of this problems?




Here is my current configuration of fortigate and ap wireless router.


fortigate : dhcp service enable in internal port. set range to .100-130

ap wireless router : dhcp service was disabled in this ap router.

Esteemed Contributor III

1:  ensure a rogue dhcp-server is not on the wire and causing issues


( if it windows you can review the ipconfig /all | findstr  dhcp  output &  if it's a macosx execute a ipconfig getpacket <interface name >    )


2: parse the config and look for 162  in the fortiOS configuration



show | grep -C 6 162.


3: FWIW If your dhcp-server sart/end is defined than your address should be in that range




PCNSE NSE StrongSwan

Select Forum Responses to become Knowledge Articles!

Select the “Nominate to Knowledge Base” button to recommend a forum post to become a knowledge article.

Top Kudoed Authors