get proxy authentication required message and failed to dial in

[PeterCheng]

Hello sir,

My scenario is: I've decided to migrate my NEC PBX to 3CX PBX and have a POC test.
Extensions in NEC is 1529 and 1530, and I also setup extension 1529 in 3CX.
3CX and NEC PBX use sip trunk to communicate with each other. NEC user can dial extension with prefix 823 to reach 3CX.
Before sending to 3CX, NEC will stripe 823, and 4-digit extension will be sent to 3CX.

And when phone(1529) in 3CX dial to extension 1530 in NEC PBX, it works, and vice versa.
But since I still have my phone 1529 in NEC PBX, and when it (1529 in NEC PBX) dials 823 1529, it failed.
when it (1530 in NEC PBX) dials 823 1529, it worked.
The only difference is 1529 appear in both sides, and 1530 only in NEC PBX.
When I use wireshark, first packet is the same INVITE from NEC to 3CX, and then TRYING from 3CX to NEC.
But then 1530 dial 8231529, the next packet is RINGING, but for 1529 in NEC PBX to 8231529, the next packet is proxy authentication required
and then the call would be dropped.

Would you mind explaining why this issue occurs and how to solve it?
Because before we remove all the phones in users' desk, they could dial to someone whose extension has been set up in 3CX.
Thanks.

Peter

 

[YiannisH_3CX]

Hi Peter,

The issue occurs because you are initiating a call and the PBX sees the TO and the FROM values and they are the same. The PBX actually thinks the extension is making a call to it self so the call fails.
With your current configuration this call will never work.

But since you are using a trunk to connect the 2 systems there might be a workaround. Add a different number in the trunk in the 3CX side and call that number. For example 55555. Then create an inbound rule that routes the call to the correct extension.

Alternatively and depending on how the NEC PBX works you could dial 8231529 on the NEC side and strip the all digits and then prepend 55555. This way you will still be dialing the same numbers but the 2 systems will do all the conversions for this to work.

 

[PeterCheng]

Hi Peter,

The issue occurs because you are initiating a call and the PBX sees the TO and the FROM values and they are the same. The PBX actually thinks the extension is making a call to it self so the call fails.
With your current configuration this call will never work.

But since you are using a trunk to connect the 2 systems there might be a workaround. Add a different number in the trunk in the 3CX side and call that number. For example 55555. Then create an inbound rule that routes the call to the correct extension.

Alternatively and depending on how the NEC PBX works you could dial 8231529 on the NEC side and strip the all digits and then prepend 55555. This way you will still be dialing the same numbers but the 2 systems will do all the conversions for this to work.

Hello Yiannis,

Thanks for your feedback.

You mean the same extension number cannot appear at both PBXs?
Let's say, 1529 has been setup at both PBXs, and if 1529 in 3CX want to find 1529 in NEC, could I design the dialing plan that if I dial 7771529 from 3CX, and when NEC receives, it strips 777 so that 1529 in NEC can ring and pick up the call?
if 1529 in NEC want to find 1529 in 3CX, could I design the dialing plan that I dial 8881529 from 3CX, and when 3CX receives, it strips 888 so that 1529 in 3CX can ring and pick up the call?

I know if I dial the same number from either PBX, it won't ring because it dials the number itself.
But now I have different prefix number in front of the extension number in other PBX.
Right now is 1529/1530 are set in 3CX, but they are also in NEC. When 1530 dials 1529, it still fails. and if I use 1531, which only in NEC and dial 1529, it works.

I will try no striping digits in NEC when 1529 dial 8231529, and let 3CX do the strip, I want to know what will happen.

Peter

 

[YiannisH_3CX]

You do not have to do this. You can dial 8881529 from the NEC and create 8881529 as a DID in 3CX under your SIP Trunk settings.
The create an inbound rule which routes 8881529 to extension 1529 and you are done.

 

[PeterCheng]

You do not have to do this. You can dial 8881529 from the NEC and create 8881529 as a DID in 3CX under your SIP Trunk settings.
The create an inbound rule which routes 8881529 to extension 1529 and you are done.

Hello Yiannis,

Thanks.
So you mean I can setup 1529 at both PBXs?
and if 1530 is also at both PBXs, can 1530 in NEC dial 1529 in 3CX?

That will be: 1530 in NEC dial 888 1529, NEC doesn't strip anything and forward all to 3CX PBX through SIP trunk. And SIP trunk in 3CX set 8881529 as DID and inbound rule set to strip 888 for called number, and it rings 1529 in 3CX, does it work?

Thanks.
Peter

 

[PeterCheng]

Hello Yiannis,

It seems not work. when user dial 8881529, and if this user's extension also set at both PBX, it will fail to call and stop after 3CX sends out proxy authentication required sip message to NEC.
May I know how to strip or remove called number for inbound call? For outbound call we can prepend or strip for called number in the outbound rule.

Thanks.

Peter

 

[PeterCheng]

You do not have to do this. You can dial 8881529 from the NEC and create 8881529 as a DID in 3CX under your SIP Trunk settings.
The create an inbound rule which routes 8881529 to extension 1529 and you are done.

Hello Yiannis,

I followed you instructions and the result is the same, so wierd.I have 8231529 as a DID in 3CX under SIP Trunk settings and inbound rule which routes 8231529 to extension 1529 now.
sip trunk setting

inbound rule

And when failed , wireshark it said proxy authentication required?


Peter

 

[YiannisH_3CX]

I see the problem. The PBX is receiving a call from number 1529 which is also an internal extension of the PBX so it tries to authenticate the extension by sending a 407 proxy authentication required. When this does not work the call is dropped.
Can you change the callers number from the NEC side? So it looks like another number is calling the 3CX PBX?

 

[PeterCheng]

I see the problem. The PBX is receiving a call from number 1529 which is also an internal extension of the PBX so it tries to authenticate the extension by sending a 407 proxy authentication required. When this does not work the call is dropped.
Can you change the callers number from the NEC side? So it looks like another number is calling the 3CX PBX?

Hello Yiannis,

Thanks.
And is it possible that when 3CX PBX receives the call, 3CX modifies the coming call's caller ID (at sip trunk?) and then 3CX won't treat is as internal call?

And one thin that you can see in the wireshark packet, why the sip message header From is sip:[email protected] and To is the same host sip: [email protected]?


Peter

 

[YiannisH_3CX]

Thanks.
And is it possible that when 3CX PBX receives the call, 3CX modifies the coming call's caller ID (at sip trunk?) and then 3CX won't treat is as internal call?

Not really. Since the PBX will identify that the call came from a SIP trunk it will treat it as an external call.

And one thin that you can see in the wireshark packet, why the sip message header From is sip:[email protected] and To is the same host sip: [email protected]?

That is correct and its the configuration most SIP providers use. For outbound calls from the PBX you can modify it from the outbound parameters of the SIP trunk. But if it is working i would not change it as it might break calls entirely.