Do you want to add multiple subnets to the same lan port and you use a Sonicwall appliance, router, firewall? You can follow these instructions to set up a multihome network for your TZ models by adding an address object for the new subnet, an ARP entry, and a route.
Example for 192.168.10.1/24
Under Network Menu Click Address Objects.
Name: My Secondary Subnet (or any friendly name)
Zone Assignment: LAN
Netmask: 255.255.255.0 (This is for a /24 change as needed)
Under Network Menu Click ARP
Static Arp entries > ADD
IP Address: 192.168.10.1 (use the IP you want to be your default gateway for this subnet)
Interface: X0 (Choose your current LAN port)
[x] Publish Entry
[ ] Bind Mac Address (Do not select)
Under Network Menu Click Routing
Under Route Policies choose Add
Destination: My Secondary Subnet (Or whatever you named your new Address Object)
Interface: X0 (or the port you chose in ARP setup if your LAN port was not X0)
Your new subnet should work now.
How to: Multiple LAN IPs on a single interface on Sonicwall Appliance
How to: Configuring Multiple WAN Subnets Using Static ARP with SonicOS