I have two public IP on my WAN interface. I'm trying to build two tunnels to this interface originating from the same remote router. I think I have good chances to make this work but there is a little captcha I need to solve.

on the main office WAN interface when I disable one of the IP thus changing the prefered source one of the tunnel is connected. Once we disable the working interface and reactivating the other IP (chaninging agin the prefered source) it is the other tunnel that connects.

With both tunnel activated, they are battling one against the other. So I'm pretty sure the only thing I need to solve is make sure that all traffic with a destination ip 1.1.1.1 is returning with the prefered source 1.1.1.1 and all the traffic with a destination 2.2.2.2 is going back with 2.2.2.2.

I wrote those two mangle and routing rule but it doesnt work as expected.

Perhaps something like this is what you're looking for? (forces traffic coming in on a WAN interface to pass out the same)

ros code

/ip route
add check-gateway=arp comment="Default Route - Distance 1" disabled=no distance=1 dst-address=0.0.0.0/0 gateway=wan1
add check-gateway=arp comment="Default Route - Distance 2" disabled=no distance=2 dst-address=0.0.0.0/0 gateway=wan2
add check-gateway=arp comment="Static Route - WAN1" disabled=no distance=1 dst-address=0.0.0.0/0 gateway=wan1 routing-mark=static-wan1
add check-gateway=arp comment="Static Route - WAN2" disabled=no distance=2 dst-address=0.0.0.0/0 gateway=wan2 routing-mark=static-wan2
 
/ip firewall mangle
add action=mark-connection chain=input comment="Mark new inbound connection wan1" connection-state=new disabled=no in-interface=wan1 new-connection-mark=wan1 passthrough=yes
add action=mark-connection chain=input comment="Mark new inbound connection wan2" connection-state=new disabled=no in-interface=wan2 new-connection-mark=wan2 passthrough=yes
add action=mark-routing chain=output comment="Mark new inbound route wan1" connection-mark=wan1 disabled=no new-routing-mark=static-wan1 passthrough=no
add action=mark-routing chain=output comment="Mark new inbound route wan2" connection-mark=wan2 disabled=no new-routing-mark=static-wan2 passthrough=no

Thank you omega for helping out.

I might not be clear but I'm located on the main office router with a single WAN but with two public IP assigned to it. I'm not tying to mangle on two interfaces but trying to build a rule that will make sure that my traffic coming in my router (and ending there since those are L2TP tunnels) goes out on the same interface but with the same public IP it had has the destination address and not the automatically defined prefered source of this wan interface.

Martin

Rockyboa, did you ever get an solution for this? I'm trying to do something similar (one interface, two IP addresses), and can't seem to get it to work correctly.