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Inbound SIP trunk issues

Daniel Ackerman

February 21, 2019 16:01

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Hi Guys, 

 

I am desperate for some assistance please. We took over a client quite some time ago and in the contract we said we would assist with their VOIP (this is not something we support in general). Basically, the PBX had been working fine untill their provider closed their doors and they ported to a new provider. 

 

Basically, what happens is only on the inbound calls, the trunk randomly goes dead and says "waiting for authentication". There is no pattern to this, it could be 5 times in 1 day, or 1 time in 5 days. Initially when this happened I would disable / enable the trunk and it would come back up. 

 

Something strange that I found totally by accident, is the connection will re establish if I simply open the IVR settings and click Save and apply ( no editing or anything is done at all but this brings the connection up again).

 

I have spoken to the ISP multiple times and they say it is not on their side. The client is getting very frustrated at this point and it is wasting alot of my time as well constantly having to watch the connection in an RDP session. 

 

If anyone has any advice, PLEASE let me know if you can think of anything to try and resolve this. Thank you in advance.

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5 comments

• 0
  
  Larry Neblett February 21, 2019 18:51

  Port forwarding on the router?

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  Larry Neblett February 22, 2019 12:41

  No answer to the above, so I will make some assumptions - 

  You have not stated if there is a router involved in front of the PBX. What you describe is sometimes observed when port forwarding or NAT has not been correctly implemented. If there is no port forwarding, then the ports will only stay open for a limited time before closing. If the system makes an outbound call, this action will cause the SIP port to open on order to let the traffic out and will stay open for around 30 seconds or so (depends on manufacturer) waiting for a reply. If nothing is seen before the port time expires, the port will close and no further traffic will flow until such time as a new call is originated by the PBX. 

  While the port is open, additional calls originating from either the UCM or provider can flow freely, but when the port does close, the provider will be blocked and not be able to get in. In a busy system, the port may be open for long periods, but when idle is when the trouble occurs. 

  You should check the port forwarding to insure that it is set correctly. Just because the trunk may show registered means nothing if using a register trunk. The system will register once, which then sets an expiry time meaning that it will not register again for whatever the expiry period is, usually an hour.

  If this does not help, then please advise.

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  Daniel Ackerman February 25, 2019 08:40

  Hi Gents,

   

  Sorry for the long response time, been away for a couple of days. I am not sure if I have explained myself correctly in the original post. So let me just clarify a few things. 

   

  The client has two completely separate SIP trunks, one for inbound and one for outbound. The outbound has no issues what so ever. It is the inbound that is the issue. 

   

  We have (very dangerously) disabled the PBX firewall, as well as forwarded UDP 5060 on the router and left it like that to test if it resolved any issues, which unfortunately it did not. The connection still went down. The thing that I can't understand here is that there is no pattern to the drops. It is possible (rarely) that the connection stays active for over 48 hours on a weekend when there is no traffic being generated, and then other times it can go down while the trunk is very active in peak times. It also works the other way around though.

   

  What I am trying to say here is, this does not seem to be a timeout issue due to the trunk not being active for a certain period. 

   

  Thank you again for the responses so far.

• 0
  
  Larry Neblett February 25, 2019 12:41

  Provider?

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  Larry Neblett February 25, 2019 12:58

  Provider? Also, is qualify enabled on the trunk? If so, disable it and see if any improvement. Re-enable firewall. 

   

  An inbound call from a provider usually does not require an authentication.