Help: new VOIP - 'one way no audio' issue

Hello,
Looking for some guidance on how to proceed, please - but I recognise debugging VOIP issues is not without its challenges..

Short Story
New VOIP connection.
I can make and receive calls, but there is no audio for me, on either outgoing or incoming calls. However there is normal audio at the other end, where they can hear my voice fine.

Detail
ISP: A&A
Router: Technicolor DGA4135
Phone: Panasonic KXTG6801

I have just been connected to FTTP.
having been with A&A for years, I ordered through them, and took the opportunity to port my copper phone line away from BT and over to A&A also.

FTTP working well.
As the supplied router has built-in ATA, I connected my existing old style phone, via an adapter, to the FX1 port.
A&A helped with the Telephony SIP Network and SIP profile settings on the router, and it shows it as Registered on the router settings.

https://imgur.com/JjxZ8Mk
https://imgur.com/CBQxNoJ

Picking up the phone, there is a dial tone, and I can make and receive calls, but I hear nothing. Just silence. The other end of the call can hear me talk. So I think that's a 'one way no audio' issue.

Contacted A&A support, but they have just pointed me towards their support page
which I have tried to follow through, with no joy.

But I do find the router settings somewhat opaque in meaning, and not sure which I should be changing.

Here is what I have now:
https://imgur.com/wXETozp
https://imgur.com/swo5i6R
https://imgur.com/PfiRknd


Solution?
1. Is there a setting I have missed, that may just click everything to life?
2. Is my Panasonic phone not compatible? Should I just buy a Yealink T31 or T41 from ebay, and plug that in?
(Do direct IP phones plugged into an ethernet port on the router have less problems than old phones plugged into the ATA port?)

I only need a very basic phone, and just the ability to make and receive calls occasionally, so no fancy features required. But I do need it to work!

Very grateful for any advice.

For A&A VOIP I use a Gigaset N300 DECT base station and Gigaset DECT phones.

The N300 has an ethernet connection to a broadband router. I use this configuration at two locations. They both work OK.

Sounds like a codec issue. I've used both gigaset and fritzbox with A&A
Make sure your codec is set to g.711a

Do you mean here?
https://imgur.com/1oEBMdu

The only options are PCMA, PCMU and G729

In reply to a post by iDoccy:

Do you mean here?
https://imgur.com/1oEBMdu

The only options are PCMA, PCMU and G729

Yes. I believe PCMA is the same as g.711 a law. Is that what you had set?

A&a only support g.711a. anything else won't work (to be honest I believe it would stop the call from connecting as it should negotiate the codec during call setup)

Yes, set to PCMA

In reply to a post by iDoccy:

Short Story
New VOIP connection.
I can make and receive calls, but there is no audio for me, on either outgoing or incoming calls. However there is normal audio at the other end, where they can hear my voice fine.

without more information i am unable to help further

the issue is the RTP is being blocked, or the ATA is not sending out the correct IP, as the phone you call can hear you the outbound traffic is ok, your issue is the inbound RTP

Okay. What is the RTP and how do I unblock it?! : )

That is a UDP protocol
SIP initiates the call, but the audio is through UDP on a different port. Your router firewall is probably blocking it - why I don't know.
I did a google and found another page on Thinkbroadband forum, pointing here:
https://support.aa.net.uk/DGA0122_VoIP

you may need to SSH into the router to make this change if this model supports that...

And the forum page this relates to.
https://forums.thinkbroadband.com/voip/f/4689093-tec...

The other option is trying the SIP ALG Helper - I saw it was disabled in your screenshots. I have it disabled, but it might be easier to try enabling it first to see if this fixes the problem before trying the undoubtably nerviness inducing CLI option !

Thanks.
But getting an error message saying Invalid path, when I try and enter those ssh commands with Putty:


engineer>set InternetGatewayDevice.Services.VoiceService.1.VoiceProfile.1.RTP.LocalPortMin 5000
InternetGatewayDevice.Services.VoiceService.1.VoiceProfile.1.RTP.LocalPortMin: 9005 fault [invalid path InternetGatewayDevice.Services.VoiceService.{i}.VoiceProfile.{i}.RTP.]
engineer>set InternetGatewayDevice.Services.VoiceService.1.VoiceProfile.1.RTP.LocalPortMax 5098
InternetGatewayDevice.Services.VoiceService.1.VoiceProfile.1.RTP.LocalPortMax: 9005 fault [invalid path InternetGatewayDevice.Services.VoiceService.{i}.VoiceProfile.{i}.RTP.]

In reply to a post by iDoccy:

Hello,
Looking for some guidance on how to proceed, please - but I recognise debugging VOIP issues is not without its challenges..

Short Story
New VOIP connection.
I can make and receive calls, but there is no audio for me, on either outgoing or incoming calls. However there is normal audio at the other end, where they can hear my voice fine.

By and large, if you can ring both ways, I would make the working assumption that most of the internet settings you are looking at are irrelevant. The worst internet issue you could have is a port blocked in a firewall.

In reply to a post by iDoccy:

Detail
ISP: A&A
Router: Technicolor DGA4135
Phone: Panasonic KXTG6801

Either find a full manual for the router or send it to land fill and get another router. Sorry to be so brutal, but without a proper manual, it is not for for purpose and A&A should not be offering it. It lets them down.

In reply to a post by iDoccy:

I have just been connected to FTTP.
having been with A&A for years, I ordered through them, and took the opportunity to port my copper phone line away from BT and over to A&A also.

FTTP working well.
As the supplied router has built-in ATA, I connected my existing old style phone, via an adapter, to the FX1 port.
A&A helped with the Telephony SIP Network and SIP profile settings on the router, and it shows it as Registered on the router settings.

https://imgur.com/JjxZ8Mk
https://imgur.com/CBQxNoJ

Picking up the phone, there is a dial tone, and I can make and receive calls, but I hear nothing. Just silence. The other end of the call can hear me talk. So I think that's a 'one way no audio' issue.

Contacted A&A support, but they have just pointed me towards their support page
which I have tried to follow through, with no joy.

But I do find the router settings somewhat opaque in meaning, and not sure which I should be changing.

Here is what I have now:
https://imgur.com/wXETozp
https://imgur.com/swo5i6R
https://imgur.com/PfiRknd

Yes, not to worry about those. The phone rings end to end both ways, so apart from firewalls, I think the internet side is working fine. This looks more like a question of codecs. Without a manual, you need to poke through the router settings systematically. Or find some kit with a manual

In reply to a post by iDoccy:

Solution?
1. Is there a setting I have missed, that may just click everything to life?
2. Is my Panasonic phone not compatible? Should I just buy a Yealink T31 or T41 from ebay, and plug that in?
(Do direct IP phones plugged into an ethernet port on the router have less problems than old phones plugged into the ATA port?)

I only need a very basic phone, and just the ability to make and receive calls occasionally, so no fancy features required. But I do need it to work!

Very grateful for any advice.

If you are looking to buy something else, then yes, a proper ethernet phone or and ATA if you have more than 1 phone.

Thanks.
Is a SIP phone more likely to work 'out of the box'?
There are Yealink T41 on ebay for not much £

No experience of yealink. I have a grandstream internet phone and an ATA. Neither worked out of the box, but they are not expected to. Both got better results than you have when configured with SIP provider settings [ie I got both ways communication] and further tinkering resolved other evident issues.

Okay, might have to try that then. Ta.

In reply to a post by iDoccy:

Okay, might have to try that then. Ta.

Download a decent VoIP softphone client and test using that before you throw the baby out with the bathwater

If FTTP, VOIP and router is supplied by A&A then surely they could give some more assistance?

I've had issues with 3 way calls with A&A VOIP and I've been told by them "NAT is evil". I don't have broadband from A&A and use NAT.

Would using the DGA router with a FXS port mean the VOIP aspect is not using NAT?

It does sound like (sorry - pun) that some of the messages are missing - hence the silence.

Lots of suggestions posted here, please excuse me if I start from the beginning:

1) You have FTTP for A&A. Are they using CGNAT? If so, you may have a problem. It seems that the A&A Help page has some suggestions on how to overcome this.

2) If the call sets up, then the codec selection is not an issue. If the codecs at either end were incompatible, the call would not even set up correctly.

3) the fact that you can hear outbound voice but not inbound suggests that the RTP packets don't traverse a NAT somewhere. I assume that the phone plugs into the FXS port on the router, so the SIP client in the router should access the internet directly and there should be no need for NAT traversal in the router itself. So, I would suspect that the problem is down to CGNAT in the network

The A&A support page that you have linked explains the iussue with NAT in some detail and makes suggestions for what you can try, whether it works remains to be seen.

I too have VoIP and FTTP from A&A, previously their FTTC with my BT line and number transferred to A&A.

When I took out the FTTP on a minimum 12 month contract, I took the option of a Technicolor DGA0122 Router for the cost of the carriage. This router has two Analogue Phone ports.

I can see from their Support Site that they discontinued supplying this router December 2024 and have since supplied the DGA4135 which you have.

I recently had an intermittent problem and rather than power cycle the router, I contacted A&A.

They tried to log in to the router, but couldn't, so asked me to power cycle. They then logged in and found OK and to date the problem has gone away. (It related to some incoming calls not ringing but being put through to be recorded.)

May be worth asking A&A to remotely log in to the router and check out?

Cheers!

In reply to a post by essex_man:

1) You have FTTP for A&A. Are they using CGNAT? If so, you may have a problem. It seems that the A&A Help page has some suggestions on how to overcome this.

AAISP is one of the most technically competant ISPs in the UK offering internet access and VoIP services. They have excellent support, especially if you get broadband and voice from them.

They do not CGNAT and every customer has v4 and v6 “proper internet”, and they are very critical of companies that don’t supply IPv6 to customers.

Edited by jchamier (Wed 29-Jan-25 22:25:39)

Hi,

This is almost certainly a firewall issue.

Fixing this will require you (or someone) to understand what range of RTP ports has been configured for VoIP and confirm that the firewall on the router has been configured to accept the same range.

I don't know whether the router will use IPv4 or v6 for VoIP and whether these are configured together or differently in the firewall - you may also need to understand that as well.

You get exactly the same symptom if NAT is blocking the incoming RTP stream (hence the existence of NAT ALGs). NAT will not be a problem here (unless the router has been configured in a very weird way to provide NAT to itself) as the router will have its own public IP address.