how to redirect VPN traffic to the correct network

RouterOS Beginner Basics
1

I have a mikrotik RB750Gr3 configured with 2 wan providers like the diagram shows
https://imgur.com/7y58SD9

1 WAN configured with DHCP and another with PPoE and failover configured. The main link is the DHCP WAN and we do not have a public IP. There is only public IP on the PPoE link.

I want to redirect all VPN traffic to the PPoE link. So, how do I do this? When I make a connection on the VPN, mikrotik redirects all traffic to the primary link and I can’t connect.

I can only connect when the primary link (DHCP WAN) is disabled.

2

If it’s just for VPN server, something like this should work:

/ip firewall mangle
add chain=input in-interface=<PPPoE interface> connection-state=new action=mark-connection new-connection-mark=conn_pppoe
add chain=output connection-mark=conn_pppoe action=mark-routing new-routing-mark=wan_pppoe
/ip route
add dst-address=0.0.0.0/0 gateway=<PPPoE interface> routing-mark=wan_pppoe