thank you for the fast repsone. my fear is someone will try to target the TD-W9970 and reconfigure it from the wan side. i like to use the TD-W9970 as a modem and connect it to the Archer C5400X. or...

by Using TP-Link TD-W9970 as bridge mode will it make the router/modem vulnerability to Wan attacks or the only way to get to the router firmware and configure it is from the Lan side ?