topic Do 48 block VOIP/SIP connections? in Internet

Do 48 block VOIP/SIP connections?

TesK4580 — Wed, 17 Sep 2025 12:48:55 GMT

I'm using my 48.ie SIM in a 4G router after my fiber connection went down and everything seemed fine at first.

Then I noticed that my Gigaset VOIP phone couldn't connect. I have 6 SIP accounts with 3 providers and all failed to connect. I tried various softphones on Windows and none could make a call (all could log on and only one custom app from the provider could start a call). I then tried eir and Vodafone SIMs and everything worked as before. I looked into various NAT settings but nothing would make VOIP work through 48.

MicroSIP for Windows shows a 403-Forbidden error when starting a caall but that's the nearest I could get to an error code.

Is 48.ie somehow blocking SIP connections?

Re: VOIP/SIP blocked?

dalyer — Wed, 17 Sep 2025 12:48:29 GMT

Is normal internet access via the 4G router with the 48 SIM installed working ok?

You may need to contact 48 support about this issue as I've never seen it raised/discussed here on the Community Forum over many years.

To contact 48 support see the links in my signature below.

Re: VOIP/SIP blocked?

TesK4580 — Wed, 17 Sep 2025 12:57:56 GMT

Everything else works just fine. All smart devices appear to work as before. It's not a CGNAT issue as eveyrthing works fine with eir and Vodafone who both use CGNAT. I tried two routers even and both give the same result.

Re: Do 48 block VOIP/SIP connections?

TesK4580 — Thu, 18 Sep 2025 14:29:14 GMT

I emailed the 48 support desk and the answer was that the service is only intended for use by smartphones. Any use of the SIM in any other 4G/5G-enabled device, such as a router, is not supported.

No indication if SIP is explicitly blocked or forbidden or if CGNAT works differently. In case anyone is curious I tried Linphone on a smartphone thru WiFi thru the router with the 48 SIM and I could at least make a call. I didn't test any further.

Would be good to hear if anyone else has something like a Gigaset VOIP basestation working with 48.

Re: VOIP/SIP blocked?

dalyer — Thu, 18 Sep 2025 15:58:01 GMT

I don't know if there's anything of use/relevance here?

https://confusedbird.com/printthread.php?tid=309

Re: VOIP/SIP blocked?

TesK4580 — Thu, 18 Sep 2025 16:42:30 GMT

Thanks for that.

It looks like it could be the same issue I'm facing. This user tried port 8060 instead of the default 5060 which works with eir and Vodafone. I'll give it a try in a few days and if it works I'll report back here.

Re: Do 48 block VOIP/SIP connections?

TesK4580 — Sun, 21 Sep 2025 14:20:09 GMT

I've tried changing ports from 5060 to 8060, STUN on/off, proxy on/off and nothing worked. When I revert back to eir fiber everything worked even with one port still set to 8060.

So, no VOIP/SIP for me with 48.ie unlike with eir and Vodafone.

I'll have to pop the 48 SIM in a phone and try some softphone apps. However, according to what I read in the phone linked to elsewhere in the thread, this shouldn't make a difference as 48 are not allowed to discriminate against certain IP traffic because of EU net neutrality rules.