https://under-linux.org/f131343-pcc-...links-por-m4d3
podese usar apartir da Mk 3.23 pode se usar o pcc tem topico bem detalhado ate como fazer em brigde so tem que alterar onde tem o gateway= ethlink colocar o pppoe .
Em rotas
add comment="" disabled=no distance=2 dst-address=0.0.0.0/0 gateway=EthLinkA scope=30 target-scope=10
add comment="" disabled=no distance=3 dst-address=0.0.0.0/0 gateway=EthLinkB scope=30 target-scope=10
add comment="" disabled=no distance=4 dst-address=0.0.0.0/0 gateway=EthLinkC scope=30 target-scope=10
add comment="" disabled=no distance=1 dst-address=0.0.0.0/0 gateway=EthLinkA routing-mark=to_nra
add comment="" disabled=no distance=1 dst-address=0.0.0.0/0 gateway=EthLinkB routing-mark=to_nrb
add comment="" disabled=no distance=1 dst-address=0.0.0.0/0 gateway=EthLinkC routing-mark=to_nrc