Encontrou isto!
Firmware versão 6.1 ou superior:
:ppp relay flush
:ppp flush
:eth flush
:atm flush
:atm phonebook flush
:eth bridge ifdelete intf=ethport4
:eth ifadd intf=eth_wan
:eth ifconfig intf=eth_wan dest=ethif4
:eth ifattach intf=eth_wan
:ip ifadd intf=ip_wan_eth dest=eth_wan
:ip ifconfig intf=ip_wan_eth status=up
:ip ifconfig intf=ip_wan_eth hwaddr=00:11:42:0c:65:1d <-- This line is only needed if you need MAC address cloning
:ip ifattach intf=ip_wan_eth
:nat ifconfig intf=ip_wan_eth translation=enabled
:dhcp client ifadd intf=ip_wan_eth
:dhcp client ifconfig intf=ip_wan_eth metric=5 dnsmetric=5
:dhcp client rqoptions add intf=ip_wan_eth option=dhcp-lease-time
:dhcp client rqoptions add intf=ip_wan_eth option=dhcp-renewal-time
:dhcp client rqoptions add intf=ip_wan_eth option=dhcp-rebinding-time
:dhcp client rqoptions add intf=ip_wan_eth option=subnet-mask
:dhcp client rqoptions add intf=ip_wan_eth option=classless-static-routes
:dhcp client rqoptions add intf=ip_wan_eth option=default-routers
:dhcp client rqoptions add intf=ip_wan_eth option=classfull-static-routes
:dhcp client rqoptions add intf=ip_wan_eth option=domain-name-servers
:dhcp client ifattach intf=ip_wan_eth
:saveall
Funciona brilhantemente. Graças ao link , lembre-se de atualizar o firmware!