2nd PPPOE connection over eth2

my ISP provides two PPPOE logins: one for dynamic ipv6/64 and one for static ipv6/54 address pool. I can in principle login both at the same time.
I want to dedicate one subnet to the dynamic ipv6 range and another one to the static one.
Can anyone give me a hint how to do? Just adding a second WAN interface over loci to eth2 seems not to work.