Majority routers will need to express forwarding feature to be disabled to work with Firewalla.
To disable the feature:
- Connect a computer to the Wi-Fi network from your Linksys router.
- Open a web browser and log in to your router's management interface at linksyssmartwifi.com
- Select 'Connectivity' and then the 'Administration' tab on the top right side of the screen.
- Uncheck the Express Forwarding box in the middle of the screen
- Click 'Apply' to save this setting and reboot your router.