Just some follow up foot notes left out yesterday and observations from the final configuration. Everything still working OK after 24 hours. Since the start of experiment from yesterday morning till now, there have been five changes to the external IP address with the last change being a renewal. This did not impact test calls made throughout the last 24 hours from mobile phone to home and CLID has worked well for all calls. Reasonably confident it would continue subject to unforeseen interruptions.
1. Fritz!Box WAN was configured for Cable Modem connection.
2. When the Telstra modem was connected directly to NBN HFC modem - messages to SIP Registrar used IPV6 addresses. Connections made through Fritz!Box show the Telstra SIP Registrar messages using the assigned IPV4 address which is expected as it is using a static IPV4 address as its WAN. The Fritz!Box log also shows its external WAN IPV6 connection and Prefix being assigned, updated and then cleared (with prefix no longer valid comment) which was interesting as I did not configure the Fritz!Box for IPV6.
3. I activated "Permit independent port sharing for this device" - fixed IP address for Telstra modem. I think that may be a UPnP setting for any devices or Apps connected to the Telstra modem. Incoming and outgoing calls worked with it OFF and ON yesterday, so I left in ON in case the Apple TV and other devices connected to the Telstra modem needed it.
4. Prior to the Port Forward 5060 implementation, around noon yesterday there is an unexpected log entry in the Telstra modem which shows the IPV4 static lease for the Telstra modem from the Fritz!Box (192.168.188.23) being set for 864,000 seconds = 10 days. Haven't seen that lease time period before in any previous Log entries.
All seems fine.
Thanks for going to such lengths to help figure this out but I've just about given up on this, I believe I have everything set up how you've explained but just with an Optus router and I just couldn't get it working.
Although, did you set the LAN IP of your Telstra Modem to a different subnet?
I had set it to the same subnet as the fritzbox
The only thing I can't be sure of is the fritzbox specific settings as I can't remember what they were called off the top of my head but I had follow that weblink provide by @YetAnotherAcc with option #2
I had checked the port forwarding after making those changes and I had green lights on them.
Yes, two different subnets, so Double NAT but that didn't present any issues for me as I am not a sophisticated high end user and acknowledge that it may be an issue for others.
Arris HFC Modem --- WAN (on LAN1 after config) Fritz!Box [192.168.188.1] LAN2 ----- WAN Telstra Modem [192.168.0.1]. That way I didn't need to change any IP address settings in each unit and dismantled after test. I have left all settings in the Fritz!Box per the test configuration with Port Forward entries but it has been returned to its storage box.
Previously when I had the Fritz!Box as a secondary router, I had to configure its LAN port 1 to a WAN port - selection was 'working through another network', it auto changed itself from default 192.168.178.1 to 192.168.188.1, so I had assumed it reserved its default address for standard DSL operations only. Maybe the Port Forward 5060 only works in two subnets as the Fritz!Box may reserve port 5060 for its own VoIP when there is only one network.
I assume you can get your Fritz!Box 7490 to connect to the internet through the NBN with its RJ45 cable into LAN1 and its network is the factory 192.168.178.0/24. If this is so the please do the following.
You can also always reach our technical teams via the My Optus App if you have any questions. However as the Fritz!Box is not a product we offer, we're unable to guarantee the products performance.
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Hi everyone - just a typo correction - realised this morning my Fritz!Box is on Firmware Version 07.21 which was released on 17 September 2020 and not the previous version 07.12 which I had incorrectly referenced in my post. Whirlpool.net.au has an interesting discussion group on AVM modems - seems that AVM release weekly Lab Beta versions which currently have a prefix 07.24-xxxxx code ID, so maybe a new General Release is pending soon. The only mention of a Telephony enhancement I picked up in the Beta versions was for Encryption setting which is available for three German carriers.