Call transfer/divert problem

[GBC_James]

Hi
3Cx V18 Update 4 running on a Windows Server 2019 Standard box on prem (well actually in a data centre 5 miles away)

Sorry if thi is the wrong place for this post. Wasn't too sure where to put it.
We have an odd problem that began last week. No changes were mad to our pbx. Our users have a number at another authority that they have to transfer calls to regularly. Everything has been fine for years with this.
Now, we are unable to transfer calls to this number, or divert an extension to it. BUT, we can call the number directly. This problem only occurs when transferring or diverting.
When you try to transfer, it just fails, either in the web client or on a handset. You just get taken back to the dial pad and call info and the caller is still on the line with you.
I looked in the event log and all I see is this;
Call or Registration to *********** @(Ln.10000@Gamma (Single Instance only)) has failed. 88.215.63.9 replied: 404 Not Found; from IP:88.215.63.9:5060
Any ideas?
Thanks
James

 

[ThomasD_3CX]

Hello,

Can you try changing under Sip Trunks > Edit Gamma Sip Trunk > Outbound Parameters (tab) > Sip Header "From:User Part" from "Originator Caller ID" to "Outbound Caller ID" ?

 

[GBC_James]

Hello,

Can you try changing under Sip Trunks > Edit Gamma Sip Trunk > Outbound Parameters (tab) > Sip Header "From:User Part" from "Originator Caller ID" to "Outbound Caller ID" ?

Thanks for Replying Thomas.
Sadly, that didn't make any difference.

 

[leejor]

It may very well be a caller ID issue, your provider not liking the caller ID being sent, when doing a transfer, or forward. But since it was a 404 not found reply, I would compare (in the Activity Log) the dialed number being sent on a transferred call, with that of a working call, when the number is dialed directly. Are they the same?

 

[ThomasD_3CX]

Can you set an outbound caller ID on the outbound rule level and try again ?
(DID that is bound to your account)

 

[GBC_James]

Hi
Sorry for the late reply.
I am actually in the office today and tried doing a direct call and a transfer to the troublesome external number, using a physical desk phone and manually dialing the number.
I could do a direct call to the number without any problems.
But when I tried the transfer, I was only able to dial the first 8 digits (11 in total) and a message appeared on the handset screen "Temporarily unavailable"
I have a capture if you want to take a look. It's too big to attach though

 

[GBC_James]

Also, we have the same outbound caller id set for all extensions already. It's the same number system wide. No personal extension numbers are allowed to have their own caller id.

 

[GBC_James]

I have just given an extension it's own caller id (so not the global id) and it has the same problem when dialling that particular external number.
It's weird because it seems to be just this one number

 

[leejor]

when I tried the transfer, I was only able to dial the first 8 digits (11 in total) and a message appeared on the handset screen "Temporarily unavailable"

Going by this, I'm going to assume (perhaps incorrectly) that the 8 digits matched an outbound rule, and that called number "as-is" was passed to your provider. If the digits sent were not valid (incomplete) , then that would explain the "not found" message from your provider. You would have to confirm this in the Activity Log. You X'd out the number sent in your first post. Check again and see if it is the same as a working call.

 

[GBC_James]

Going by this, I'm going to assume (perhaps incorrectly) that the 8 digits matched an outbound rule, and that called number "as-is" was passed to your provider. If the digits sent were not valid (incomplete) , then that would explain the "not found" message from your provider. You would have to confirm this in the Activity Log. You X'd out the number sent in your first post. Check again and see if it is the same as a working call.

Hi
So the number i am dialling (in the uk) i don't mind posting it, it's not mine is 01329824399
If i dial that number directly, there is no problem.
But if I try transferring a call to this same number, as I type the number in, i get to 01329824 and then before I can finish the message on the phone (yealink T42) says "Temporarily Unavailable"
If there was an outbound rule problem, surely I wouldn't be able to dial this number at all, is that not right?

 

[leejor]

It may be something to do with the transfer process, on the set itself. Does the transferred call even reach the outbound rules/provider?

Is it just this one number, any number with the same areacode, or any outside transfer at all?

 

[GBC_James]

It may be something to do with the transfer process, on the set itself. Does the transferred call even reach the outbound rules/provider?

Is it just this one number, any number with the same areacode, or any outside transfer at all?

I get the exact same results on aphysical handset, the mobile app, web client or windows client.
It's only this number. I have another number at the same external location, same area code etc that we can call just fine.

It's driving me crazy, this one.

 

[GBC_James]

Hi,
I am clocking off for the weekend, will check in again Monday.
Thanks for helping, guys

 

[GBC_James]

Hi, here's an update.
I finally had a conversation with an IT guy at the other end of the call. He says that they recently moved from an old Mitel PBX to using MS Teams for calls. They had all their ddi's ported from BT (uk) to Gamma.
It turns out the number we can successfully transfer calls to their end is not yet a Teams number but is still on the old Mitel pbx.
He gave me a number in his IT dept which is on Teams, and I can't transfer to that one either, but I can call it directly.
So, am I right in saying MS Teams is the smoking gun here?

 

[leejor]

Well, it's obviously something to do with the calls going to the Teams numbers, but why it is failing, is the big question. Could it be caller ID? The solution may involve the use of Wireshark, and getting someone involved the can analyze the call at the far end, if possible

 

[GBC_James]

Hi again,
So after alot of investigating, I discovered that the Phone divert problem was user error. After I had set the extensions to divert to the problematic external number, the helpful users had come along and switched their extensions to voicemail! Which they dont have access too! hence call failure.
After putting this right, I found that diverting an extension works. Great.

But the transfer of calls to the external number still fails.
I finally got a meeting with the IT guys from the external authority we are trying to transfer to, and they set up a meeting with the consultant who helped them migrate to gamma and Teams. He offered to look at some log dumps in wireshark and he found a problem with Re-invites and SDP.
Which is abit beyond my level.

I have attached a snippet of his email if you want to rake a look.
Basically SDP info is missing.
Their end, as part of the security their SBC, they have the below configuration in place.

REMOTE RE-INVITE : supported only with SDP

He suggests forward this information through to our telephony support provider, requesting that they amend so that Re-INVITES are sent with SDP details included. This issue will then be resolved.

So is that something I need to do within 3CX, or is he talking about contacting our SIP provider Gamma and getting them to amend settings?

 

[GBC_James]

Ok, so messing around before I clock off for the weekend, I was looking at the settings for Our Sip Trunk to Gamma, and I found the setting "Supports Re-Invite"
Thsi setting was ticked, and therefore ON/Active.
I turned it off, and the problem is now resolved.
Hooray.

Can anyone foresee a problem with leaving this setting off?

 

[leejor]

You may just have to wait and see if any other issues, for other call scenarios, crop up.