Open your browser and go to 192.168.20.1
Note: There are currently two firmware versions for this router, if yours is the latest one (blue background) just set as follows:
Otherwise if it has the older menu then proceed with the steps below.
Step 1: Advanced Setup > WAN Service
Step 2: Remove all Entries
Step 3: Advanced Setup > Layer2 Interface > ETH Interface
Step 4: Tick and remove all the entries in here
Step 5: Advanced Setup > WAN Service click add
Step 6: Click IP over Ethernet and click next.
Step 7: Select Enable IPv4 for this service and Optain an IP address Automatically:
Step 8: Select Enable NAT and Enable Firewall:
Step 9: Ensure ETH is listed under 'Selected Default Gateway Interfaces'