Hello, this guide should be easily adaptable for even a different Internet Gateway. The steps below is tailored for v14 TL-WR841N and Omada L3 SG3428X Switch for demonstration purpose. I also have a video link at the bottom of this post if you would like to see it in action. The TL-WR841N does NOT support 802.1Q so it can not create different VLANs, This Internet router is an entry level router and officially supports only a "flat network" on its LAN.

Goal:

• Demonstrate separation of responsibility between WAN/Firewall/VPN/etc. router vs LAN router

Use Case:

• Use Omada Switch and Access Point with a non-Omada Internet Gateway/Firewall/VPN/etc.

Note:

• For demonstration purpose, I am using a $19 TL-WR841N as my Non-Omada Gateway (NOG)
• The same "general" idea can applied to other L3 devices (see below for "Extra Tip for Non-Omada L3 Set Up")

Assumption:

• Omada L3 SG3428X Switch is configured/set up and running.
• Default VLAN 1 as Management VLAN for Omada
• Default LAN IP for WR841N

IP Network and VLANs

• LAN - 192.168.0.1 - non-Omada Gateway WR841N
• VLAN 1 - 192.168.0.100 - Omada SG3428X (MAC xx:xx:xx:xx)
• VLAN 10 - 192.168.10.X - Omada SG3428X SVI
• VLAN 20 - 192.168.20.X - Omada SG3428X SVI

Omada Prerequisite

1. Identify L3 Switch IP
   Devices > Omada Switch > IP Address > 192.168.0.100
2. Identify all L2 VLANs defined in L3 Switch that needs access to Internet
   Settings > Wired Network > LAN > VLAN 10 > 192.168.10.0
   Settings > Wired Network > LAN > VLAN 20 > 192.168.20.0
3. Identify port/vlan of Omada with Profile "All" [or Profile VLAN 1]
   Devices > Switch > Ports > Port 1 : Profile All (or Profile VLAN 1)

Non-Omada Gateway WR841N Set Up

1. Configure basic WR841N settings
   Operation Mode > Wireless Router
   Network > LAN > IP Address: 192.168.0.1 > Subnet Mask: 255.255.255.0
2. Other than 192.168.0.0 make sure no IP network repetition/conflict between Omada SVIs and WR841N IP Networks
3. Add all Omada IP networks (Step 2 of Omada Prerequisite) as Static Route pointing to Omada L3 Switch IP as "Next Hop" (Step 1 of Omada Prerequisite)
   Advanced Routing > Static Route List > Add New > Destination IP Address : 192.168.10.0 >  Subnet Mask: 255.255.255.0 > Gateway : 192.168.0.100 > Status : Enabled > Save
   Advanced Routing > Static Route List > Add New > Destination IP Address : 192.168.20.0 >  Subnet Mask: 255.255.255.0 > Gateway : 192.168.0.100 > Status : Enabled > Save
4. Reserve an unused WR841N LAN Port 4
5. Connect WR841N LAN Port 4 to the Omada Switch Port (Step 3 of Omada Prerequisite)
6. Optional: DHCP IP Reservation for SG3428X of 192.168.10.100
   DHCP > Address Reservation > Add New > MAC Address  xx:xx:xx:xx > IP Address : 192.168.0.100
   Recommended: Assign static IP for SG3428X of 192.168.10.100

Omada L3 Set Up

1. Optional: Reboot

Testing

1. Configure any Switch port as VLAN 10 or VLAN 20 access ports
2. Plug any PC. It should get either VLAN 10 or VLAN 20 IP address
3. Ping WR841N IP 192.168.0.1. It should reply.

Omada Verification

1. Insights > Routing Table > Switch > SG3428X > Destination IP/Subnets: 00.0.0/0. > Next Hop: 192.168.0.1 > Distance: 254

Extra Tip for Non-Omada-L3 Set Up

1. Optional: A static route to 0.0.0.0.0 with next hop to NOG IP 192.168.0.1 can be manually configured if the network device doesn't automatically detect/assign this.

If you would like to see this in action, you can refer to diagram below for this video.