WDS across vLANS not working

I am having problems getting WDS to work across VLANs. PCs within the same VLAN can use WDS with no problem, but when I try to use WDS across VLANs, I get the following error:

```

304 11.304373 {WDS.IP} {CLIENT.IP} TFTP 64 Error Code, Code: Illegal TFTP Operation, Message: Access violation.

```

I've tried the following while troubleshooting:

• Disabling the firewall on the WDS server.
• Confirmed that WDS is set to reply to ALL clients.
• Creating a policy that allows ALL traffic from the troubled VLAN to the WDS server.
• Move the VM between VLANS (works while in the same VLAN as the WDS server, but does not when I move it back).

None of this changed the behaviour. I keep getting the same error.

I have the correct DHCP options:

• Next bootstrap server {WDS.IP.ADDRESS}
• DHCP Option 66 : String : {WDS.IP.ADDRESS}
• Set the filename with the following command:

  set filename "smsboot\\x64\\wdsmgfw.efi"

No matter what I do, I keep getting the same message and problem.

Has anyone been able to get WDS to work across VLANs?

I'm running FortiOS v6.2