I hope you mean you used a cat5 cable between ONT and laptop.
I plug it to LAN port 4. I never with any other port though (I believe port 2-4 should be working).
When I connected LAN port 4 to my wireless router (WAN port), it wont be able to get internet connection. And I can only connect LAN port 1 to wireless router. I suspect LAN port 1 is the only port that able to have internet connection (forget the networking term for that).
In your laptop, set:
gateway: 192.168.100.1
ip address: 192.168.100.2 (any number from 2-254)
subnet: 255.255.255.0
Try to ping 192.168.100.1 -t
If you can get reply, means the ONT default IP is 192.168.100.1
and once you are connected, login via web browser
username: root
password: admin
Play at your own risk