I have TPG FTTC and an ASUS DSL-AC68U and the solution posted by @bigRED worked perfect for me.
When I had ADLS2 the ASUS worked great in our 3 storey town house (modem on ground floor with 96% signal on top floor). But when we switched to FTTC and had to use the supplied router from TPG it's just typical ISP supplied junk hardware and was lucky to get 60% signal upstairs.
An additional step I did was factory reset the ASUS because I had previously played around trying to get it working and had changed a few of the settings.
The only negative is I have 3 devices for a simple internet connection. Not that big a deal as they are tucked away out of sight but I might look at Optus 5G home broadband if I need to change anything.
THis is probably a bit late, but I gather ASUS lock VLan ID2 for some other purpose. I have no idea why TPG still use VLan tagging other than no one told them it is not necessary if you have a wan connection from an NBN device. Even wanting the username and log in for the first connection is bizare. Its not as though someone else can come in and hook up to your fixed line in your house. I can only assume it is because they have completly unskilled staff in their tech area and so they use the one modem/router for everyone with the preconfigured settings. I just want a router that doesn't drop to half speed every day until I reboot.
That worked because it is a modem/Router and they all have Vlan settings. But for FTTC you only need a router and if you didn't already have one, why pay more for one with a modem that you don't need. The best I can figure out is that with the router only version you have to go into the IPTV settings and pretend you are setting up for IPTV so you can then allocate VLan tag to lan ports you pick. Even Telstra doesn't need Vlan tagging and definatley no log in or Vlan with aussie broadband. Try and use the new google wifi nest mesh router. No Vlan setting on it. SO you already have an NBN modem (termination device), then you have to keep that bit of garbage Archer VR1600V as a DHCP server and use your google as an access point. There clearly is noone in the marketing department saying how can we provide a better service to customers.
What we provide for our NBN services are TP Link Archer VR1600 modem/router and TP Link C1200 router.
You can use any type of router so long as it is NBN compatible.
We do not recommend any brand and it is best to check with a professional at an electronic store as to which one would suit your internet needs. (Wi-Fi consideration, modem speed etc)
It's would be best if you know what type of NBN service is available at your address. May we know if you are an existing TPG customer? If yes, please send us a private message with your account details so we can have a look.