As the DSL-AC88U contains the Broadcom (BCM) 63138 modem chipset, which supports both VDSL2, G.INP and the currently being tested by BT Open Reach G.fast, I have provided a short guide on how to configure the DSL-AC88U to work as a modem (Bridge Mode)
The DSL-AC88U supports bridge mode, but does not support VLAN ID (802.1q) whilst in bridge mode, the VLAN ID has to be handled by the connecting router .
Login to ASUS Router User Interface (UI)
Go to Advanced Setting > WAN > WAN Type – Select DSL/Ethernet (VDSL) for FTTC Connections
PVC Setting > WAN Connection Type – Select Bridge
Enable WAN Radial Button – YES
802.1q > Enable – Select NO (VLAN ID does not work for Bridge mode)
In a completely sane world, madness is the only freedom (J.G.Ballard).