Hi Guys,

Do you know if I can use a ER605 (TL-R605) router with Telstra NBN and still have 4G Failover and access to SIP/Telephony that comes from Telstra Smart Modem?

Topology is

NBN Connection Box > Telstra Smart Modem > TPLINK Switches and APs

I've tried to do the following

NBN Connection Box > TPlink ER605 (TL-R605) > TPLink switches and APs ( This works but loose 4G failover and SIP/Telephony that is supplied by Smart Modem)

Troubleshooting done

* If put Smart Modem in Bridge mode loose 4G failover and Telephony

* Attempted DMZ via Smart Modem but believe can't get it to work.

* Routers connected but on different subnet's but I don't believe it worked properly.

Any suggestions. If not is there another method to get a WAN failover connected via the ER605 (TL-R605). Telephony might I could possibly port to another provider or divert to my mobile. It's more the 4G failover I would like to keep.

Thanks

Shane