[Bug] GL-RM1 fails to obtain DHCP lease on specific VLAN

Running into a weird issue with my Comet GL-RM1 where it won't get a DHCP lease on one VLAN but works perfectly on another. Both VLANs are set up the same way from a firewall and routing perspective.

Setup:

GL.iNet Comet GL-RM1

  • UniFi UCG-Max gateway

  • UniFi USW-Lite-8-PoE switch

  • Zone-based firewall, both VLANs in the same internal zone

Works fine on VLAN 10 (192.168.10.x); broken on VLAN 99 (192.168.99.x), DHCP range .100-.200 for both.

What happens on VLAN 99:

  • Shows up in UniFi client list with a 169.254 self-assigned address

  • Packet capture shows the gateway sending ARP requests with no reply from the Comet

  • Tried setting a static IP directly on the device — still unreachable, still no ARP reply

What I've ruled out:

  • Switch port — Native VLAN 99, Tagged Block All, correct

  • DHCP — server enabled, valid range, auto gateway on

  • The VLAN itself — plugged a Windows laptop into the exact same port the Comet was on and it pulled a 192.168.99.x address immediately with no issues

  • The device — works perfectly on VLAN 10

So the VLAN is fine, the port is fine, the Comet just doesn't seem to like this subnet for some reason. Anyone seen this before?

Could you please export the logs and send them our way?