At the moment IPFire detects the needed interface for a static routing automatically.
Sometime that’s bad…
What about an optional filed for the interface at the “Static Routes” menu? Is this possible?
Why would that be bad?
If you have a complex design it can happen that IPFire thinks it can reach a network over the red interface, even the correct way is the green interface
That can only be the case when you have multiple subnets connected to the same switches on IPFire is only in one of them. Just give IPFire another IP address from that subnet and you are fine.
The system should not decide to go out the wrong interface as long as you have a consistent routing configuration.
If you have different ways out to the world (internet, second router with VPN like the German Konnektor for doctors,…) it can happen.
There are a lot of really complex situations a standard algorithm can’t handle.