In fact, I’d like to specify rules based on bandwidth in use on the channel instead that only relative wheights (I’d like to use WAN2 only if capacity on WAN1 exceeds 80% of its limit that is specified in the QoS “Global Bandwidth” settings), and then also alternate WAN on the same client-server if necessary.
Basically this would require a new mode let’s name it ‘Overflow and fail-over’
I think the script you need to look at is nb_setnexthop.
You may need to change the script that once the bandwidth hit 80% then all new traffic will use next gateway. The next question you should answer is about logic used if you have 3 or more GW and how to deal after all GW are in overflow mode.