I'm using nlbwmon to track my bandwidth usage per internal client. That's all working fine, and usage per local client is something I already consider solved adequately.
However, I'm looking down the road to set up mwan3, which has the capability to choose between my multiple gateways based on remote destination and not only internal source (which is something I have configured now for my three gateways). When I get there, it would be very helpful for me to have some record as well of usage per remote IP range.
A look around the existing bandwidth monitoring resources, and some quick Googling, haven't revealed a clear answer. This seems to me like it could be a common enough use case that someone may already have solved it. Is there a tool available that does this conveniently already, or a walk-through for how to set something up?