2 WANs using PPPoE on same eth interface

Hi,

My first question 

I'm using an Ubuiquiti EdgeMax Lite (3 eth ports) and I would like to ask you if there is possible this type of topology:

eth0 - no ip address

pppoe0 - is using eth0  (ip 1.1.1.1)

pppoe1 - is using eth0  (ip 1.1.1.2)

pppoe0 has NAT to eth1

pppoe1 has NAT to eth2

I would like to make an insulation,

PPPoE0 -> 1.1.1.1 - eth1

PPPoe1 -> 1.1.1.2 - eth2

Is this possible?

And my second question:

Eth1 has 172.30.0.0/24

Eth2 has 172.31.0.0/24 

Eth1 is in vlan id - 10

Eth2 is in vlan id - 20

How come I can ping and connect from eth1 to an ip address that belongs to eth2?

Thanks