Solved. I leave the solution for someone else. One of the 2 WAN had a wrong MTU set. After I set the right MTU I had the expected performance.

Model : Hardware Version : Firmware Version : ISP : Hello, I have the router TL-R470T+ with 2 WANs. The first is 55/20Mbps and the second is 30/3Mbps. The maximum aggregate speed that I reach is...

Model : Hardware Version : Not Clear Firmware Version : ISP : Hello, I have a network with 2 gateways and I would like to load balance them using the TP 470. The addressed of the 2 gateways are :...