DHCP Issue Between Two Subnets
One of my clients migrated some equipment and ended up moving a separate network onto their older firewall (TZ300 - Firmware v18.104.22.168-11n). That network used to be behind a router that is now removed. Currently I have two separate LANs behind the firewall (X0 - 192.168.4.0/24 & X3 - 192.168.5.0/24). The X0 LAN is the internal corporate network and X3 is a Resident network. The X3 interface on the firewall is the gateway for that network. They have a Ubiquiti PoE switch and about 16 access points on the X3 network. All of those access points and the end users used to receive their DHCP addresses from a server on the X0 network (192.168.4.5). Since the move they are no longer able to receive DHCP. I didn't think I would have to put a direct route between the X3 and X0 subnets since they are both designated as LAN and a local route should exist. Do I need to update some access rules or configure a direct route to that server from the X3 subnet?
Try creating a new Zone (eg: guest) and setting that as the Zone for Interface X3.
Having 'guest' and corporate LANs co-mingling in the same zone is not good practice. Also look into IP Helper (a.k.a. DHCP Relay) on the Sonicwall.