How to approach QoS for 2 subnets, NAT-ed behind a Mikrotik

Hopefully, this shall be the last topic regarding this QoS issue that I have.

In this topic, I’d like to discuss the possible approaches for a very common scenario, IMHO.

The Scenario:

-2 subnets, NAT behind Mikrotik RB450G
-one ISP connection with MIR external 2mbps down/1mbps up metropolitan 100mbps down/20mbps up.
-no guaranteed bandwidth, bandwith CIR is at 128kbps if I recall correctly

The Goal:

-decent performance for both subnets at the same time
-use the bandwidth as efficient as possible , shaping everything down to 2mbps down/1mbps up
doesn’t look like a viable option


Which are the possible QoS approaches for this scenario?