Strange Softphone behaviour on Iphone

[abrown]

Hello, new to 3CX today so please bear with me.

We are an experienced Cloud MSP who are trialling 3CX, I initially set up a 3CX server on a raspberry pi on an internal network, and found that it worked fine when two iPhones were on the WIFI could call each other and hear no issues.

However, if one or both of the phones were on 4G (no wifi, i.e. external) then errors started happening. OK, first thoughts Firewall issue...

Checked all that then it got really strange.

If one phone was on Wifi and one was on 4G. Then the following happened.

1. 4G phone initiates a call, WIFI phone answers, works ok. audio works. no problems.
2. WIFI phone initiates a call, 4G phone answers, The call does not connect, suggesting the SIP message has not made it to the WIFI phone.

Put this down to a firewall or raspberry Pi issue or NAT issue.

I spun up a new Server in AWS Lightsail, All installed without issue. with an external Static IP. All settings working as expected. Re-registered the iPhone softphones on the sip.

But again, the same thing. Now Wifi is still external (my wifi connected to the internet, not to AWS) So I wouldn't have expected any issue.

But still, if the iPhone is on 4G connection, it can not answer a call. Put it on the WIFI and answer the call no issues...

I can't work this out, can't be firewall issue as now the server is in AWS. and when on 4G there are no firewall or NAT issues...

Just wondering if anyone has any suggestions as to why or what is going on? Known Bug?

iPhone 6S, IOS 12.2, 3CX ver: 15.5.18.472

All downloaded and installed today, so I'm stumped... Any pointers would be welcomed.

 

[cobaltit]

Absolutely can be a firewall/NAT issue. Could be carrier grade NAT on the 4G side or other issues. Try it with the tunnel enabled and see if you still have issues.

 

[abrown]

Thanks for the response Cobaltit, For sure it could still be a carrier firewall issue, I meant that I had removed my LAN Firewall from the equation.

3CX Tunnel is already enabled on the iPhone app.

 

[abrown]

Further information:

Bit more testing this morning.

Set up 1 x webclient extension, plus 1 iPhone 3cx extension.

When iPhone is on the Wifi all works fine, able to answer inbound, make calls to the web client. audio clear and present.

But, soon as the iPhone with 3CX app is on 4G (UK EE Network, full signal strength and speed tested)
I can make calls from the phone to web client and all works.
But can NOT accept incoming, sometimes it will simply not answer, sometimes it will answer but no audio...

Now to prove this is not an issue on the EE network, i run another SIP providers phone app client, that works without any issue in both directions. same location, same signal strength extra...

Could do with some help otherwise 3cx is going to be a non-starter for us. sure its some simple UE...

 

[JohnS_3CX]

Hi @abrown,

Please follow this conversation https://www.3cx.com/community/threa...-place-call-from-one-client-to-another.61277/

 

[abrown]

Further update, Just spoken to out Account Manager who helped me identify the issue.

Its because when on 4G most of the UK network operators are now using IP6...

There is a patch, which I am just about to raise a support ticket to get details on.

SO hopefully resolved shortly.

 

[Vali_3CX]

@abrown
According to the feedback we've got, the EE IPv6 issue seems to be solved by beta iOS client (available since two months ago), so you may give it a try.