Solved Can't get calls in or out with Yealink T21P E2

[Comp4all.ca]

Hi all,

I have an issue with a specific customer.
Their PBX is hosted on a private cloud installed on Debian 10 with the latest version of 3CX v18.

Everything worked fine up until 3 days ago.
My customer gets his internet from the building and according to them, they have changed anything.
I can see that the device is registering but it takes the device a long time to be registered.
I add a 2nd phone there Grandstream 2601P and it's not able to register at all.

When I plug it in my office there are no issues.

the building internet is the provider, we added a router to manage the clinic and NAT is enabled and all ports are open.
The building IT insist they haven't changed anything but we were not able to get any phone working there.
They are reluctant to open the 3CX ports saying nothing is blocked.

Any idea on what we can check?

 

[JohnS_3CX]

Hello,

I think you should start by installing an SBC in their office, which is probably the best way you can "control" for any network variables that could be messing with SIP traffic.

 

[leejor]

The building IT insist they haven't changed anything but we were not able to get any phone working there.

People don't like to admit that something was changed, (or, they may not be aware that someone else made changes), this way they simply say, "it's your problem, not mine". Since you don't have control of the remote router, you are probably never going to know what is happening between the ISP and the set. Assume that someone changed something, perhaps for another customer in the building, and try the SBC. You could also try using a 3CX app, over local Wifi, to quickly verify that a Tunnel connection gets through.

 

[Comp4all.ca]

Hello,

I think you should start by installing an SBC in their office, which is probably the best way you can "control" for any network variables that could be messing with SIP traffic.

Thank you, John.

I did offer it as a solution.
They don't want to be dependent on a computer for calls. if the installed SBC goes down the phone won't work.

 

[Comp4all.ca]

People don't like to admit that something was changed, (or, they may not be aware that someone else made changes), this way they simply say, "it's your problem, not mine". Since you don't have control of the remote router, you are probably never going to know what is happening between the ISP and the set. Assume that someone changed something, perhaps for another customer in the building, and try the SBC. You could also try using a 3CX app, over local Wifi, to quickly verify that a Tunnel connection gets through.

Thank you for your insights. via wifi, we are able to get calls.
And I think they changed something as now we have outgoing calls but no incoming.

 

[JohnS_3CX]

Thank you for your insights. via wifi, we are able to get calls.
And I think they changed something as now we have outgoing calls but no incoming.

I doubt they changed something. But even if they did, do you really want to rely on whether some 3rd party makes unexpected changes on the firewall all the time? This could bring down the customer's telephony at any time..

STUN has more requirements than you may initially realize, and what you describe is typical STUN behavior when the firewall is not fully under your control.

Thank you, John.

I did offer it as a solution.
They don't want to be dependent on a computer for calls. if the installed SBC goes down the phone won't work.

Now they don't work reliably at all, so an SBC will definitely be an upgrade for this situation. Relying on a single point of failure is a better option than total daily failure, and endless complaints by your customer. Perhaps if you were to explain it better they might change their mind? If you need a better explanation tell me and I will do my best to answer any questions you may have.

I think you will be very happy with our SBC stability, but if you want extra reassurance rur SBC also offers a High Availability mode too: https://www.3cx.com/docs/sbc-high-availability-cluster/


To summarise: since you have no control over the main firewall, the router you installed there will not make any difference in improving the situation and I suspect these problems will keep going on and on until the customer complains about it.

By all means, do try and sort it out if you can, but when you get tired of all the back and forth, simply get a Raspberry Pi 4B, install the SBC and these networking woes will largely disappear. The SBC was designed exactly for these types of cases and so far we have had very good feedback.

Please avoid WiFi for desk phones, it will not fare well in the long run even if it seems ok on day 1 (delays in connecting calls, drops in audio)

Let me know if I can be of further assistance!

 

[Comp4all.ca]

I doubt they changed something. But even if they did, do you really want to rely on whether some 3rd party makes unexpected changes on the firewall all the time? This could bring down the customer's telephony at any time..

STUN has more requirements than you may initially realize, and what you describe is typical STUN behavior when the firewall is not fully under your control.


Now they don't work reliably at all, so an SBC will definitely be an upgrade for this situation. Relying on a single point of failure is a better option than total daily failure, and endless complaints by your customer. Perhaps if you were to explain it better they might change their mind? If you need a better explanation tell me and I will do my best to answer any questions you may have.

I think you will be very happy with our SBC stability, but if you want extra reassurance rur SBC also offers a High Availability mode too: https://www.3cx.com/docs/sbc-high-availability-cluster/


To summarise: since you have no control over the main firewall, the router you installed there will not make any difference in improving the situation and I suspect these problems will keep going on and on until the customer complains about it.

By all means, do try and sort it out if you can, but when you get tired of all the back and forth, simply get a Raspberry Pi 4B, install the SBC and these networking woes will largely disappear. The SBC was designed exactly for these types of cases and so far we have had very good feedback.

Please avoid WiFi for desk phones, it will not fare well in the long run even if it seems ok on day 1 (delays in connecting calls, drops in audio)

Let me know if I can be of further assistance!

Thank you, John.

I hear you, I Will see if we can open ports or move to SBC,

 

[Comp4all.ca]

Hi All,

We eventually got an internet connection and now everything is working as it should.

Thank you.
Tal

 

[JohnS_3CX]

Hi Tal,

Good to hear! We will mark it as solved then