Does it do fixed line failover to mobile?

[DanMelbourne]

Does the new modem with 4G backup also have voice failover to mobile? (i.e. if the fixed line service is down, does the VoIP landline service get carried over the mobile network instead). 

[YetAnotherAcc]

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@DanMelbourne wrote:

Does the new modem with 4G backup also have voice failover to mobile? (i.e. if the fixed line service is down, does the VoIP landline service get carried over the mobile network instead). 

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I doubt that, but I would expect that the phone line would still work because VoIP is just internet data.

[DanMelbourne]

True, but Telstra's 4G modem uses VoLTE when failing voice over to 4G, which is obviously more suitable for a mobile network since the VoLTE stack is tuned for the latency and jitter of mobile networks etc. Getting that all working seamlessly requires a fair bit of engineering integration.  

[YetAnotherAcc · Accepted solution]

I just read the product release info and it seems that VoIP will not work at all.

Q: Will I have access to the same service features when using the 4G back up service? 
A: Some services or service features may not work while the Optus Ultra WiFi Modem is using the 4G back up service. This includes but is not limited to voice service (if applicable),

If you have any questions about it its bet to post it in that thread for a higher change of Optus replying to you.

[DanMelbourne]

Ahhh good find!! Thank you. That answers my question. 

[YetAnotherAcc]

Your welcome. 

Although it does answer your question I do find it unacceptable that VoIP will not work.

But Telstra using VoLTE now make more sense because 4G uses shared public IP addresses which generally breaks certain services, VoIP being one of them.