To use Firewalla in DHCP Mode, it'll require you to disable DHCP service on Routers.
For routers that don't provide an option to turn off the built-in DHCP service, here is a simple workaround.
Step 1: Connect Firewalla
Connect Firewalla to the Router. Connect Power. And wait for 5 to 7 min.
Step 2: Setup Firewalla to DHCP Mode
Launch the App, before starting to set up, pick "Manual Setup" => "DHCP Mode"
Step 3: Configure Your Router
Take Xfinity XB6 as an example here.
Login Router and Tap on Connected Devices
Step 3-1: Reserve an IP for Firewalla
Write down the IP of Firewalla, e.g. 10.0.0.237 (yours will be different)
Step 3-2: Limit DHCP
Tap on Connection->Local IP Network and limit the IP range to Firewalla IP Address (you got from step 3-1)
Original IP range:
Change both Beginning Address and Ending Address to Firewalla's IP Address:
Note: If your router does not allow you to create a DHCP range with the same start and end address, you'll need to reserve an IP address for a fake device.
In this example:
Set DHCP Beginning Address: 10.0.0.237, DHCP Ending Address: 10.0.0.238. Then reserve IP Address 10.0.0.237 for Firewalla, and also reserve IP Address 10.0.0.238 for a fake device with a mac address that is not in your network.
Step 4: Done
Now you may need to reboot or wait for devices to start getting the 192.168.218.x address.
Notes on IPv6:
Some providers don't allow the router to fully disable or limit IPv6. When this happens, Firewalla will not be able to manage any site that's IPv6. Resulting you can't see traffic or block any IPv6 sites. We are working on a solution, this may take a while. Example, if you block Firewalla.com it will work, but block google.com will not.