Fortigate can't get IP from ISP using DHCP

[Lephongrap]

Hello everyone,
I'm facing a problem when trying to connect from my ISP to Fortigate 60F via DHCP.
ISP can't allocate IP or Fortigate can't get IP from ISP,
I tried connecting from ISP to another PC and router and everything works fine.
I did a factory reset but it still doesn't work.
Do we have a solution?

FortiGate 

[vsahu]

Hello,

Please take the below debug on Fortigate :

diag debug reset

diag debug console timestamp enable
diag debug application dhcpc -1
diag debug enable

Change the Interface to manual and save it, revert it to DHCP let the debug run for 30 sec, and share the output.

To disable the debug use the below command:
diag debug disable

[Lephongrap]

Hi Vsahu,
the above command uses CLI window, can I copy and paste them to run?

[vsahu]

Hello Phong Le,

Yes just copy and paste the command to run, once it's in place, Change the Interface to manual and save it, revert it to DHCP let the debug run for 30 sec, and share the output.

[Lephongrap]

Hello vsahu,

I did it,

But it's still no working

[mgoswami]

Hi Phong,

Please share the output of the commands here. You can copy and paste the output.

BR,

Manosh

[Lephongrap]

Hi Manosh,
You mean this :

Thanks,

[Cajuntank]

I ran into a similar situation the other day with a new T-Mobile backup connection I plugged into my FortiGate. I connected my laptop (wired) and it worked fine. When I plugged that into my firewall, it would not get an IP via DHCP. I power cycled their antenna/modem device and then was give an IP address to my firewall. So thinking their antenna "married" itself to the first MAC address that connect to it and did not like swapping to another without a antenna/modem reboot with the new device (firewall) already connected. Worth a try.

[Toshi_Esumi]

For T-Mo's device, or any other 4G/5G termination devices like Cradlepoints, it probably has "IPPassthrough" setting by default, which relays IP from the carrier's GW to the device behind the termination device. In those cases, DHCP server is on the carrier side and it doesn't know when something is swapped on the LAN side of the termination device.

So you need to take the 4G/5G connection down once to pull the IP again to a swapped LAN device.

Toshi