I'm trying to determine how our MX router with DPCE modules (non-trio) is identifying flows for load-balancing. I've seen documention that states when you are exporting a load-balancing policy to the forwarding table, the default data points it uses for the hash include incoming ifindex + src IP + dst IP. If so, wouldn't the router select the same interface it received the initial packet on as it's outgoing interface for the return traffic of that flow (keeping bidirectional traffic of the same flow on the same interface)?
I'm seeing some behavior on one of our routers that indicates otherwise - ie. incoming traffic of one flow coming in on one interface and the outgoing return traffic of the same flow using another interface.
What am I missing?