@shano81 Hi

I'm not very familiar with Telstra Modem, you have two Modems? Or actually one of them is just a "Router"? I tried to search online and figure out the NBN Modem is just a fiber modem actually.

Anyway if you only have one Internet source, then only need one Modem(I believe it should be the NBN modem).

Connect the ER605 WAN port to the Modem and it should work. The “Smart Modem" you can still configure it as Access Point and link it to ER605's/switch's LAN port.

  @Somnus 

The following setup I have

* NBN Connection box has an ethernet cable that goes to the Telstra router (Telstra Smart Modem Gen 2) which has 4G failover and SIP for my home handset (phone)

* NBN Connection box to ER605 WAN port should work but I'm not sure about the impact of not going via the Telstra Smart Modem especially when comes to SIP and 4G Failover. 

* Alternatively can go NBN Connection Box to Smart Modem Gen (Put in Bridge Mode) then to ER605 WAN port. The only unknown is bridge mode and what it affects.

Thanks

Shane

  @shano81 In most of the cases Bridge Mode is to prevent double-NAT issue. （like a router connected to another router)

Some Modem is Modem Router 2-in-1 device, and "bridge mode" means disable the built-in router function to let it work as a pure modem.

My strong recommendation would be to directly connect ER605 to the NBN modem and skip the Telstra smart modem completely.

You can re-direct your telephone number to your mobile via the Telstra website, no extra charge to do it.

Telstra ia also an IPv4 and IPv6 ISP.

So don't forget to enable IPv6.

Set WAN to DHCPv6 and LAN to SLAAC + RDNSS for proper Telstra setup.

  @add1n1 

Thanks for the Advice. The phone never gets used so happy to do that but the Telstra router has a 4G failover that would be handy to still use when internet goes down.

Shane

  @add1n1 @shano81 

  Be aware when enabling ipv6 on the ER605 is there is no firewall options for ipv6. I am still looking for a way to configure that but so far have not been able to. You will be reliant on your Device's software firewall.

See the following feature request.

https://community.tp-link.com/en/business/forum/topic/274222