GL-MT300Nv2 Tethering Failover

I am trying to setup my GL-MT300Nv2 for LAN and 3G/4G. As discussed in other topics, it detects my Huawei modem as Tethering, which is fine - as long as it works.

However, my question is. When the modem boots it uses my LAN and the traffic through my external modem (tether) is minimal. When I unplug my ethernet cable to test the fail over, that works successfully too.

But, when I plug my ethernet cable back in, after a minute or so I can see that uses LAN again, but traffic through my modem stays very very high “as if” both connections are utilised. I don’t understand why there should be any traffic going through the tethering connection?


What is the traffic?

I’m not sure how to figure that out?