I have a 6350 SR LTE router that I am trying to set up as a backup internet source for my home. I have set up everything and all works well. Except that my internet speeds through the WAN port is limited to 120Mbps (I currently have 600Mpbs cable internet). I have checked and tried several settings but still get the limited 120Mbps on WAN port. Is this device capable of the full 600Mbps on the WAN port?