Welcome to the Kitz forum.
You are currently trying to perform the impossible. The default configuration of an
Openreach supplied
HG612 is to act as a
bridge between the
LAN1 port and the
xDSL port (a.k.a. the WAN port).
In that configuration, the
Home Hub provides the
PPPoE login credentials. It is impossible to "login" twice to the same service. It is a similar situation to attempting to plug in two ADSL modem/routers to one line. As, I'm sure you realise, that will not work.
Now If you would like to use both LAN ports of the
HG612, then it, the
HG612, will need to be configured to provide the
PPPoE credentials and act as a
DHCP server to the two LAN ports.
Finally you will need to set the
Home Hub into
pure bridge mode . . .
I'm just not too sure.
Now where is
Asbokid? He is
bound to have an idea!