Zyxel IES 1000 / AAM1212-51 splitting traffic over two ethernet ports
The idea is very simple: Traffic from ADSL ports 1 to 6 should go over ethernet port #1 and traffic from ADSL ports 7 to 12 should go over ethernet port #2.
To achieve this behavior, VLANs must be used. I just created two VLANs (1 and 2) and assigned the desired ports as "untagged", thats it. In fact, from outside the device you won't see any VLAN tags as VLAN is just used to create two independant port groups.
Don't forget so do a config save after successful configuration, otherwise configuration will be lost after reboot.
The screenshots provide a configuration walk through: