As you may have heard, once (if) NBN ever rolls out in your area, the objective is to decommission the ageing copper infrastructure used by Telephony / Fax / ADSL / Alarms etc and move/port your existing telephone number over to your NBN carrier.

The following is a case study based on Telstra residential and the issues we faced in using a 3rd party router in place of the Telstra Supplied DLINK DEVG2020 or the Technicolor TG797 or later.

Firstly, you need a working NBN Service. For this example we are using FTTN. Single PSTN telephone line being ported to VOIP. So connect a Cat5 ethernet cable to the NBN NTU into port UNI-D1 only.

This cable then will connect to the WAN port on your telstra supplied modem.

As we all know the Telstra routers are very basic, and if you wish to retain your existing router setup telstra will not support you with VOIP settings or help. There are many solutions out there regarding Bridge-mode etc, but these will NOT allow you to retain your voice component of the service.

Out of the box if you plug your Telstra supplied Technicolor or DEVG router in, it will auto configure (we assume based on MAC address) and within 10minutes your PSTN land line will be ported to VOIP and you can place and receive calls over your normal handsets. This is good. Now while this is connected, browse to the modem on 10.0.0.138 and disable DHCP and all wireless access. save and reboot. (if you need access in the future manually assign a 10.0.0.x address and plug into a LAN port on the Telstra modem).

Now simply  unplug your telstra modem and connect your own Router WAN port to the NBN Cat5 cable and reconfigure your router for Ethernet over IP. Now connect the Telstra modem WAN port into a LAN port on your router (and make sure DHCP is enabled on your router).

Because the Telstra modem has already registered and setup your telephony, it will now call out to the Telstra SIP Servers and register your phone THROUGH your other modem (disable firewall etc on your equipment first to ensure it all works).

You now have VOIP working BEHIND your own router connected directly to NBN! Congratulations!

We did recently find an interesting amendment for that article. It appears that if you don’t receive a call on your VOIP line for an ‘undetermined amount of time’ (approx. 15mins) the voip service that was registered will drop off. Calls will come in, but wont ring, and go straight to voicemail (you can dial in and collect them from voicemail though no problems), yet you can continue to make outbound calls with no issues.. If however you regularly receive calls (at least 1 every 15mins or so it works fine. Its as if there is a ‘periodic telstra registration’ requirement for phone registration on idle.

What we’ve been doing as a solution to get around this though is migrating our clients with FTTP to use UNI-V1 with battery backup and this eliminates the Supplied Telstra Modem altogether which is a much nicer solution. Plus it gives you battery backup.

For all those people who dont have FTTP (Fibre to the Premise) we needed another solution :

After running some more investigations via wireshark, we have discovered the following NAT’s that you need to open up to get the Telstra Voice to work behind a non-telstra modem.

Setup NAT’s in your internet facing router pointing to the telstra modem using :

Due to the HUGE number of phone calls and emails to us regarding this article there seems to be some confusion on how to connect up your devices in order to use the above information.

NBN coming into your premises -> (WAN) Your Router (ethernet 1) -> Telstra Router (WAN 1) -> Phones
NBN coming into your premises -> (WAN) Your Router (ethernet 2) -> Switch -> Rest of your network

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Document Published : 15 March 2016