As I'm trying to configure a new SonicWall firewall for a branch office, and am having IP Helper" (DHCP relay) issues. I'll attach picture; here's the clearest I can explain the problem:
There are two VLANs: VLAN109, for customers and VLAN110 for employee traffic. On VLAN109, the default gateway is the TZ400W’s X0 interface (192.168.109.254); on VLAN110, the layer3 switch at 192.168.110.251 is default gateway. Routing on both sends customer Internet and employee Internet traffic out through different routers.
I created a zone called “Corp” for the Employee traffic, and a “GuestWLAN” zone so I could have separate SSIDs for internal and external users. I created a sub-interface on the W0 interface for the GuestWLAN zone, and called it W0:V109. Though the TZ400W has extra ports I could configure for the Corp zone, building wiring...