In case you want to disable the LAN ports 2 - 4 to avoid that your customers receiving another DHCP IP from your DHCP server, please follow this guide.
1. You need to add a new WAN interface with IPoE. Please make sure to not use a VLAN existing on any switch, DSLAM or gateway in the WAN of the CPE
2. Create a new interface group. Here you choose the LAN ports which should be inactive. As PTM Type choose the previously created new WAN Interface