@sagar002100 what you are attempting is link aggregation/bonding/trunking. Remember that this provides multiple paths for data to travel but which does not mean that a session is alive on both links. Once a session (in laymen terms a communication with remote i.e website, terminal etc.) the session goes thru only that link so let's say you have a 100 Mbps bsnl and a 200 Mbps spectra isp, you speed would be either 200 or 100 Mbps depending on which connection the router chose as optimum. You will never get a 300 Mbps throughput. That's why link aggregation works better with multiple devices competing for bandwidth. That way devices traffic can be managed better. Anyone telling you link aggregation works is selling snakeoil. Sometime people are using routers with low performance as in the wifi speed. Suddenly they get into a better router and use link aggregation and feel the speed of internet has increased. They just don't know that their previous router was a dud :)

Fae wrote

The Load Balance feature selects which WAN port is session-based. If there is only one session with the end-point, only one WAN port will be selected to handle the traffic. When there are a lot of sessions with the end-point, the router can assign these connections to different WAN ports according to the bandwidth ratio of each WAN port. In this way, all the bandwidths of WAN links are in good use to speed up the whole traffic. This is how the load balance works on the router.

@Fae 

I'm a bit confused. When I configured a R470T+ with two WAN connections (a slow ADSL 8/1Mbps and a 4G LTE around 45/25Mbps), if I unchecked Enable Bandwidth Based Balance Routing, it gave me a merged speed. If I checked that feature, it just communicated on one of the WAN connections during the speedtest. The same happens if I check Application Optimized Routing. And what I found odd is that when I have clearly one speedy connection and another slow and nobody else is using the net at that moment, the router doesn't give me the faster connection, even if I set the values correctly about upstream and downstream for the WAN ports.

So, what's the point enabling Bandwidth Based Balance Routing?

Does R470T+ work as same way as R600, the way you described above?

What happens when there are dozens of devices through an Easy Smart switch hanging on the net (browsing, chatting, streaming etc.) and I leave that feature unchecked?

@sagar002100 This router is not working with load balancing , I have 3 WANs and only routes by the 3rd one, there's no way it works like 480 or 470