Why non-approved phones can't use VoWiFi on 2degrees

Forums › 2degrees (including Slingshot, Orcon, Flip, Stuff Fibre, MyRepublic, 2talk and Vocus) › Why non-approved phones can't use VoWiFi on 2degrees — the technical proof

andyit

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#324734 18-May-2026 16:37

After two months of investigation into why my Redmi Note 10 Pro would not connect to VoWiFi on 2degrees despite being fully capable hardware, I've found the root cause. I'm posting this for anyone who hits the same wall.

My phone works perfectly on 2degrees for VoLTE after enabling via dialer code. VoWiFi however fails every time with "turn off airplane mode or connect to a wireless network." The carrier config on the device shows carrier_wfc_ims_available_bool = false.

2degrees support spent two months telling me the device was not supported without ever explaining why.

Today I purchased a One NZ prepay SIM for $12. Using identical hardware, identical WiFi, identical dialer codes — VoWiFi connected immediately on One NZ. Seamless handover between WiFi and cellular works perfectly. Same phone. Same WiFi. Different carrier. Different result.

Thanks to another poster @boosacnoodle, they commented that it was due to 2D using a non standard gateway address. So I thought I would test it and this what I found.

The GSMA specification defines a standard domain name format for ePDG gateways (the server that handles VoWiFi connections):

epdg.epc.mnc{MNC}.mcc{MCC}.pub.3gppnetwork.org

Any phone following the GSMA standard automatically looks for VoWiFi at this address. I tested both NZ carriers:

One NZ (MNC=05) — GSMA standard address: nslookup epdg.epc.mnc005.mcc530.pub.3gppnetwork.org

The result was that it resolves to three IP addresses.

Then tried 2degrees (MNC=24) — GSMA standard address:

nslookup epdg.epc.mnc024.mcc530.pub.3gppnetwork.org

The result NXDOMAIN — does not exist.

Using 2degrees actual ePDG address: nslookup epdg.ims.2degrees.net.nz

The result is that it resolves to 118.149.14.20

So what this means is 2degrees operates their VoWiFi gateway at a proprietary non-standard address rather than the GSMA standard location. One NZ and other carriers follow the GSMA standard.

Any phone following the GSMA specification — which is the default for every phone not specifically configured for 2degrees — cannot automatically find 2degrees' VoWiFi gateway. To use VoWiFi on 2degrees a phone must be specifically configured with their proprietary address, which only happens through 2degrees' device certification process.

This is independently verifiable by anyone using the two nslookup commands above.

As an aside during investigation, UDP port 500 (IKE/ISAKMP — the port used to establish VoWiFi tunnels) was confirmed reachable at 2degrees' ePDG gateway: nc -vzu -w 5 epdg.ims.2degrees.net.nz 500

The result was that connection succeeded. This confirms the gateway is reachable and operational — the barrier is device configuration, not network availability.

Conclusion

VoWiFi on 2degrees requires device-specific configuration to their non-standard ePDG address. This configuration is only applied through their certification process. Phones not on their certified list — regardless of hardware capability — cannot complete VoWiFi authentication because they are looking for the gateway at the GSMA standard address where 2degrees does not exist.

One NZ follows the GSMA standard, which is why the same hardware connects immediately without device-specific configuration.

All tests above are reproducible by anyone with a device on either network and the Termux app installed.

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Max
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#3493497 18-May-2026 18:04

Hmm...

Not sure how much I agree with that, considering when I was a Oneplus 12 user and on 2degrees, VoWiFi worked just fine both in NZ and when I was abroad in 2024 December enjoying Tokyo.
Considering if you dip into the modem files for Oneplus devices 9 and newer, under I believe the experimental folder there are 3 folders for the big 3 here. Yes there are configurations present for all 3. Which was frequently mentioned in your previous thread.

I also used a Pixel 7a (not listed but shares the same SoC as the 7 and 7 Pro so technically yes but no) and also a Pixel 9 Pro XL(not actually officially supported) and VoWiFi works there too. So I've used two phones not on their certified list, however VoWiFi worked fine.

I'll quote @SaltyNZ here:

The great thing about SIP is that there are about a thousand ways to do the same thing.

The terrible thing about SIP is that there are about a thousand ways to do the same thing.

So yes whilst 2degrees does something slightly different because there are a thousand ways to do the same thing.. but if the phone is built for it and has the configuration then yes it will just work.

I'm not going to speculate if 2degrees run a whitelist or not. Mostly because I'm not an employee there or in that team. I'm fairly certain nobody from 2degrees could answer that for commercial reasons. Why it did not work for 2degrees, I can't agree with the assessment that they whitelist only specific devices giving my above experience. Google and Oneplus especially is not sold by any of the three and has actually been a little questionable(Oneplus) when I wore the green hat in specific scenarios.

Happy to eat words if it can be confirmed officially from 2degrees.

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andyit

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#3493504 18-May-2026 18:28

Really appreciate this — genuinely useful counter evidence that refines the conclusion.

The OnePlus and Pixel examples make sense in context — if those manufacturers have included 2degrees-specific modem configurations, including presumably the correct proprietary ePDG address, then they work regardless of being on the certified list. That's the manufacturer doing the work rather than 2degrees certifying the device.

The Redmi Note 10 Pro simply doesn't have that configuration — Xiaomi hasn't included 2degrees' non-standard ePDG address in the modem files for this device. One NZ works because they follow the GSMA standard address that Xiaomi already has configured by default. It's worth noting that PBTech do sell Redmi devices in NZ and at least one model — the Redmi Note 14 — does work with 2degrees VoWiFi. However based on information shared earlier in this thread, that appears to be because 2degrees pushed a specific profile update to that device. This is consistent with the commercial arrangement theory — PBTech as an authorised reseller has the relationship with 2degrees to get that configuration deployed, whereas a Redmi device purchased outside that channel, like mine, never receives it.

So the refined empirical conclusion is: 2degrees works with any device whose manufacturer has included their proprietary ePDG configuration, certified or not. Devices without it are out of luck unless 2degrees moves to the GSMA standard address.

One observation — and I want to be clear this moves from empirical evidence into opinion — is that the OnePlus and Pixel examples raise an interesting question. Why would any manufacturer include a non-standard proprietary ePDG address for a carrier in one of the smallest markets globally unless there was a commercial incentive to do so?
My opinion, though I can't prove it, is that 2degrees has commercial arrangements with specific manufacturers to include their proprietary configuration in device firmware. Manufacturers with that arrangement work — certified or not. Manufacturers without it don't, regardless of hardware capability.
One NZ following the GSMA standard sidesteps this entirely — any standards compliant phone just works without any manufacturer needing a specific commercial arrangement with the carrier.

On the whitelist question — based on the evidence gathered I don't believe 2degrees operates a traditional IMEI whitelist. The mechanism appears more subtle than that. Because 2degrees uses a non-standard proprietary ePDG address rather than the GSMA standard, any device works if its firmware includes that address — certified or not, as your OnePlus and Pixel examples demonstrate. The effective 'gatekeeping' isn't an explicit whitelist but rather a natural consequence of their non-standard infrastructure — only devices whose manufacturers have included the proprietary address in firmware will work, and that inclusion appears to require either a commercial arrangement with 2degrees or a specific profile push through an authorised channel like PBTech.

The result is functionally similar to a whitelist but the mechanism is different — and arguably more problematic, since it's invisible to consumers and never officially disclosed.

Happy to be corrected if anyone has evidence otherwise — but that's where the logic leads me.

aj6828

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#3493505 18-May-2026 18:33

I had the same issue with my Honor 400 Pro and spent a few months trying to get VoWiFi going on 2degrees. One NZ / Mighty worked fine straight out of the box on the same phone. VoLTE worked on 2degrees, but WiFi Calling never would.

I tried Pixel IMS + Shizuku back then to force some IMS settings, and then one day WiFi Calling just randomly started working out of nowhere. No phone change, same network, same setup.

So for sure I think there’s something in how they provision the connection or apply the carrier config. Your findings are really interesting because I was starting to wonder if it was more of a provisioning / carrier config issue rather than a hardware limitation.

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andyit

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#3493507 18-May-2026 18:40

Really interesting experience, thanks for sharing it. The Honor 400 Pro working on One NZ but not 2degrees is entirely consistent with the GSMA standard ePDG address finding.

The 'randomly started working' detail is fascinating but I honestly can't explain it without speculating — and I've tried to keep this thread to reproducible evidence rather than theory. It does suggest the situation is more complex than any single explanation covers.

What's clear from multiple people's experience is that One NZ works where 2degrees doesn't on the same hardware. The nslookup tests explain at least part of why. Beyond that I'll leave it to people with actual 2D network access to fill in the gaps.

tangerz

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#3493543 18-May-2026 21:16

aj6828:

I had the same issue with my Honor 400 Pro and spent a few months trying to get VoWiFi going on 2degrees. One NZ / Mighty worked fine straight out of the box on the same phone. VoLTE worked on 2degrees, but WiFi Calling never would.

I tried Pixel IMS + Shizuku back then to force some IMS settings, and then one day WiFi Calling just randomly started working out of nowhere. No phone change, same network, same setup.

So for sure I think there’s something in how they provision the connection or apply the carrier config. Your findings are really interesting because I was starting to wonder if it was more of a provisioning / carrier config issue rather than a hardware limitation.

Is it possible this occurred after a firmware update that included the necessary 2Degrees VoWiFi profile?

KiwiSurfer

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#3493547 18-May-2026 21:30

andyit:

One NZ (MNC=05) — GSMA standard address: nslookup epdg.epc.mnc005.mcc530.pub.3gppnetwork.org

One NZ is MNC 01 not 05...

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#3493549 18-May-2026 21:42

KiwiSurfer:

andyit:

One NZ (MNC=05) — GSMA standard address: nslookup epdg.epc.mnc005.mcc530.pub.3gppnetwork.org

One NZ is MNC 01 not 05...

I really hope we didn't use AI to structure both the OP and that hallucination.

I would also like to understand the thinking when this was written up...

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Oblivian

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#3493555 18-May-2026 22:12

It's like de-ja-vu

https://www.geekzone.co.nz/forums.asp?forumid=97&topicid=298485&page_no=21#3173222

boosacnoodle

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#3493557 18-May-2026 22:22

Yep. You can try make a CNAME in your router/dns for epdg.epc.mnc024.mcc530.pub.3gppnetwork.org to the custom server and see if it works. Won't make your device "supported" but may give you some idea of why it is/isn't working.

andyit

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#3493649 19-May-2026 06:33

One NZ is MNC 01 not 05...

-------

I really hope we didn't use AI to structure both the OP and that hallucination.

I would also like to understand the thinking when this was written up...

Fair correction on the MNC — One NZ is 01 not 05. That was my error. I've rerun the test with the correct value you quoted:

nslookup epdg.epc.mnc001.mcc530.pub.3gppnetwork.org

Result: Resolves to 203.96.213.192 and 203.96.213.193

So the conclusion remains unchanged — One NZ publishes their ePDG gateway at the GSMA standard address, 2degrees does not. The MNC error was mine and I should have verified it before posting. I'll update the original post with the corrected test. Thanks again for the correction it is all useful to help find the cause.

andyit

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#3493650 19-May-2026 06:37

boosacnoodle:

Yep. You can try make a CNAME in your router/dns for epdg.epc.mnc024.mcc530.pub.3gppnetwork.org to the custom server and see if it works. Won't make your device "supported" but may give you some idea of why it is/isn't working.

Yes that's an option but to be honest, after the months of 2D tier 1 and 2 support telliing me I needed to replace my phone rather than engaging with the reason, it is far easier, and cheaper to spend $2 on a one.nz SIM and change service providers.

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nztim

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#3493664 19-May-2026 08:20

If the phone has the carrier profile in its software it will just work, I am tired of these threads 😉

Any views expressed on these forums are my own and don't necessarily reflect those of my employer.

andyit

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#3493682 19-May-2026 08:56

The phone does have the GSMA standard address. VoWiFi works on one.nz and spark but does not on 2D due to the non standard GSMA address used.

I offer this as a description of the problem, testing, causative factors and the solution for anyone in a similar situation which I thought was the whole point of these forums.

hamish225

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#3493800 19-May-2026 16:05

That's actually really interesting and good to know. Thanks for posting this. I wonder why 2D decided to go for the non-standard address?

At some point you would expect carriers to be following standards rather than making things hard, right?

*Insert big spe*dtest result here*

Jase2985

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#3493814 19-May-2026 16:28

andyit:

The phone does have the GSMA standard address. VoWiFi works on one.nz and spark but does not on 2D due to the non standard GSMA address used.

yes but you keep skipping over the fact it doesn't have the 2 degrees ones because they are non default ones, they chose to use non-standard ones so It's up to them and the device manufactures to include them so the devices would work on their network.

Time to build a bridge

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