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

1 | 2 | 3

27 posts

Geek
+1 received by user: 18

#3493819 19-May-2026 16:39

Jase2985:

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

Completely agree — which is exactly what I said in the post. 2degrees chose non-standard addresses, manufacturers who have commercial arrangements with 2degrees include them, others don't. The solution was a $2 One NZ SIM. Bridge well and truly built. 😄

andyit

27 posts

Geek
+1 received by user: 18

#3493834 19-May-2026 17:20

hamish225:

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?

Thanks — glad it's useful. The honest answer is we don't know why 2degrees chose a non-standard address. It could be a legacy decision from when they launched before GSMA standardisation was widely adopted, or it could be a deliberate commercial choice — the practical effect either way is that only devices specifically configured for their address work, which creates a dependency on their certification process.

One NZ following the standard means any GSMA compliant phone just works without anyone needing to do anything special. As you say, that's how it should be.

Hopefully 2degrees moves to the standard address at some point — it would instantly open their network to a much wider range of devices and eliminate this problem entirely. Whether there's commercial appetite to do that is another question entirely.

Oblivian

7374 posts

Uber Geek
+1 received by user: 2143

ID Verified

#3493840 19-May-2026 17:47

Fwiw it appears spark also have a standard but not, internal fallback in their config.

epdg.epc.mnc005.mcc530.pub.3gppnetwork.spark.co.nz has rdns to the same IPs as .org

andyit

27 posts

Geek
+1 received by user: 18

#3493841 19-May-2026 17:51

Oblivian:

Fwiw it appears spark also have a standard but not, internal fallback in their config.

epdg.epc.mnc005.mcc530.pub.3gppnetwork.spark.co.nz has rdns to the same IPs as .org

Thats really interesting — so Spark covers both bases. The standard GSMA address works for any compliant device, and they also maintain their own internal fallback for any device configured with a Spark-specific address. Both resolve to the same infrastructure.

That's actually the right way to do it — maximum compatibility with zero downside. Any device works regardless of whether it's configured with the standard address or a Spark-specific one.

2degrees by contrast only has their proprietary address with no standard GSMA fallback — so devices configured to the standard find nothing, and only devices specifically configured for 2degrees work.

The contrast between the two approaches is fairly telling.

boosacnoodle

1394 posts

Uber Geek
+1 received by user: 931

#3493845 19-May-2026 18:10

Oblivian:

Fwiw it appears spark also have a standard but not, internal fallback in their config.

epdg.epc.mnc005.mcc530.pub.3gppnetwork.spark.co.nz has rdns to the same IPs as .org

Correct. Spark have both set-up, which is how could 2degrees could do theirs, too (yet they have elected not to).

This is certainly not the first time it has been raised with them, so I could only speculate on why they have not sorted this yet.

Linux

12369 posts

Uber Geek
+1 received by user: 8663

Trusted

Lifetime subscriber

#3493847 19-May-2026 18:20

I don't think he will be able to comment on this thread but no harm in asking @SaltyNZ

Dyson

Shop now for Dyson appliances (affiliate link).

SaltyNZ

9066 posts

Uber Geek
+1 received by user: 10072

Trusted

2degrees

Lifetime subscriber

#3493867 19-May-2026 20:05

I can tell you that we do not whitelist devices. We just don't go out of our way to make sure that devices we have not tested will always work. It is also public (and I did a quick Google search just to make sure!) that we are currently replacing our IMS core with a new one from Nokia so there may be some improvements in broader compatibility with unsupported devices when that goes live.

iPad Pro 11" + iPhone 15 Pro Max + 2degrees 4tw!

These comments are my own and do not represent the opinions of 2degrees.

Linux

12369 posts

Uber Geek
+1 received by user: 8663

Trusted

Lifetime subscriber

#3493868 19-May-2026 20:10

@SaltyNZ thanks for posting really appreciated

I was going to mention that 2degrees is replacing part of its core network and changes could happen after that but I would be guessing

Now everyone has it from the horses mouth! 100% factual

insane

3330 posts

Uber Geek
+1 received by user: 1010

ID Verified

Trusted

2degrees

Subscriber

#3494088 20-May-2026 16:22

andyit:

.... 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...

......

Hi Andy,

2degrees does follow the standard, a quick DNS lookup against the hostnames returns valid results pointing to the same IP. How did you test? Perhaps check from a different Wifi connection in case something is interfering with your lookups.

> epdg.epc.mnc024.mcc530.pub.3gppnetwork.org
Server: dns.google
Address: 8.8.8.8

Non-authoritative answer:
Name: epdg.epc.mnc024.mcc530.pub.3gppnetwork.org
Address: 118.149.14.20

> epdg.ims.2degrees.net.nz
Server: dns.google
Address: 8.8.8.8

Non-authoritative answer:
Name: epdg.ims.2degrees.net.nz
Address: 118.149.14.20

From our DMs you can see I checked pretty much everything possible, but glad your device had the necessary config embedded for another carrier before it lost manufacturer support/updates.

andyit

27 posts

Geek
+1 received by user: 18

#3494105 20-May-2026 17:53

I appreciate you checking, however I need to be precise about the timeline. I ran this exact test two days ago using identical parameters — resolver 8.8.8.8, same hostname — and received a clear NXDOMAIN response. Today it resolves to 118.149.14.20, which is identical to the proprietary address epdg.ims.2degrees.net.nz — the same gateway, just now accessible via the standard GSMA address.

I've independently confirmed UDP 500 and 4500 both succeed on the standard address — again pointing to the same infrastructure.

However VoWiFi still fails to complete on my device on 2degrees despite DNS now resolving and both IKE ports responding. The barrier remains at the authentication layer. A $2 SIM and I am up and running on another carrier straight away.

Something changed between two days ago and today. I'll leave the timing and conclusions to others to consider.

nitro

785 posts

Ultimate Geek
+1 received by user: 346

#3494110 20-May-2026 18:20

i also did a quick check, because this is how i have Wi-Fi Calling on my access point (R750):

which works (on the AP):

HP

Shop now for HP laptops and other devices (affiliate link).

boosacnoodle

1394 posts

Uber Geek
+1 received by user: 931

#3494180 20-May-2026 20:22

insane:

Hi Andy,

2degrees does follow the standard, a quick DNS lookup against the hostnames returns valid results pointing to the same IP. How did you test? Perhaps check from a different Wifi connection in case something is interfering with your lookups.

> epdg.epc.mnc024.mcc530.pub.3gppnetwork.org
Server: dns.google
Address: 8.8.8.8

Non-authoritative answer:
Name: epdg.epc.mnc024.mcc530.pub.3gppnetwork.org
Address: 118.149.14.20

I can confirm that back in March this address did not resolve. That it now does so with no changes on my end (same for others) suggests that the issue on the GSMA end may well now be resolved. Wonder if some peoples phones now suddenly started supporting VoWiFi?

MaxineN

Max
2114 posts

Uber Geek
+1 received by user: 1734

ID Verified

Trusted

Subscriber

#3494230 20-May-2026 20:30

SaltyNZ:

I can tell you that we do not whitelist devices. We just don't go out of our way to make sure that devices we have not tested will always work. It is also public (and I did a quick Google search just to make sure!) that we are currently replacing our IMS core with a new one from Nokia so there may be some improvements in broader compatibility with unsupported devices when that goes live.

I am very pleased to not be eating my words.

Good luck!

Ramblings from a mysterious lady who's into tech. Warning I may often create zingers.

Want broadband cheap and made for tech enthusiasts? Go look over at Quic. Use R177510EBNVXP for free setup at check out.

AKLWestie

652 posts

Ultimate Geek
+1 received by user: 115

Trusted

Lifetime subscriber

#3494233 20-May-2026 20:39

insane:

2degrees does follow the standard, a quick DNS lookup against the hostnames returns valid results pointing to the same IP. How did you test? Perhaps check from a different Wifi connection in case something is interfering with your lookups.

> epdg.epc.mnc024.mcc530.pub.3gppnetwork.org
Server: dns.google
Address: 8.8.8.8

Non-authoritative answer:
Name: epdg.epc.mnc024.mcc530.pub.3gppnetwork.org
Address: 118.149.14.20

> epdg.ims.2degrees.net.nz
Server: dns.google
Address: 8.8.8.8

Non-authoritative answer:
Name: epdg.ims.2degrees.net.nz
Address: 118.149.14.20

From our DMs you can see I checked pretty much everything possible, but glad your device had the necessary config embedded for another carrier before it lost manufacturer support/updates.

I did a DNS lookup of epdg.epc.mnc024.mcc530.pub.3gppnetwork.org this morning, it was not mapped to an IP address when I query it.

SaltyNZ

9066 posts

Uber Geek
+1 received by user: 10072

Trusted

2degrees

Lifetime subscriber

#3494236 20-May-2026 20:42

Well, we didn't just add it during the day, I assure you...

iPad Pro 11" + iPhone 15 Pro Max + 2degrees 4tw!

These comments are my own and do not represent the opinions of 2degrees.

1 | 2 | 3