Dual PPPoE Wan failover with specific port

RouterOS Beginner Basics
6

How should it be to handle the default gateway in the to_WAN_pppoe2 table?

/ip route
add dst-address=0.0.0.0/0 gateway="backup_PPPoE_interface"

/ip route
add dst-address=0.0.0.0/0 gateway="backup_PPPoE_interface" routing-table=to_WAN_pppoe2
open port for dualwan help