FortiOS 6.0.3 Issues with Fortigate DHCP server and Cisco WAPs

[Jim_Manley]

I updated a Fortigate 81E to FortiOS 6.0.3.  After doing so, the DHCP services to wireless devices connecting via Cisco WAPs broke.  After a bit of wiresharking it appears that the way FortiOS processes the DHCP Offer packets has changed.  In particular, the server seems to ignore the DCHP Discover's broadcast bit and sends out the DHCP Offer as a broadcast at the IP and MAC layers.  This is different than what FortiOS 5.4.4 does.  The difference is enough to impact my Cisco gear.

I've submitted a ticket along with explanation and wireshack captures to Tech Support but they've been strangely quiet about it.

Has anyone else noticed this behavior?

Thanks.

Jim

[Toshi_Esumi]

DHCP discovery is regularly ignored if you reboot the server side because after the reboot it doesn't know previous assignment for those clients. The client side needs to request a new IP when the discovery process times out.

https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol#DHCP_discovery

So that part is normal but something else must have been changed to break it.

[robinsonjas]

Jim,

Are you still having this issue? I am running UniFi WAP and have similar behavior. I can set the port to access mode and it will pull DHCP fine. I have created a ticket, did you ever get a resolution?

[Jim_Manley]

I never got a formal response from Fortinet but I did keep an eye on the Fortgate releases.  Version 6.2 had a bug fix that looked like it addressed my specific issue so I upgraded the Fortigate that had the problem and the Version 6.2 fixed the problem.  I suggest you update to Version 6.2 and see if it sorts things out for you as it did me.