2 wan from same interface

Hello,

i want to implement the following scenario.


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I have two modem/routers to site A and i want to use them to site B for load balancing/failover among with the third router located at site B.

How i can create different interfaces for the two routers coming to the same port?

PPPoE is not an option for any of these routers, it must stay NATted.

Thank you

any thoughts?

Base on your Diagram, you can use the VLAN on the switch then trunk the connection of wireless to wireless then on the site B create Vlan that you will define on the SIte A.