Need some help with a Ghost in my FreePBX system, outbound calls are dropping randomly

Hi Team,

I’m about 72 hours away from ripping the system out of this office and switching this client back to POTS.

Here’s the situation and a history:
This is a simple PBX installation. A client in the suite next door has older phones, older equipment, same service provider, less traffic, but ZERO dropped calls.
I’ve practically replaced every single piece of hardware in this office chasing this problem, but I’m still having random outbound dropped calls. Sometimes they happen after 20 seconds, sometimes they happen after 5 minutes. Sometimes they don’t happen for a couple days, sometimes we’ll get a dropped call every hour all day long.

  • Running 32bit Distro 1.814.210.58-1 on a new Dell Xeon server with enough guts to handle at least 200 concurrent calls.
  • Cisco SG300-10P PoE switch powering the SIP Phones
  • (5 phones) Cisco SPA525G2 phones running the firmware (7.4.9)
  • Peplink Balance 30, port forwarding setup correctly to PBX, QoS setup to prioritize VoIP traffic.
  • Comcast Cable Internet as the ISP, Static IP address, Notification that we pass SIP traffic on port 5060 and 10000-20000
  • VoIP Innovations as the trunking provider inbound
  • as the trunking provider for outbound. This was recommended as a first test to see if VoIP-Innovations was dropping the outbound, but drops continue with

That is a start of the information. I need to either find the smoking gun in this issue or have a trap/datalog/plan in place to capture and locate the problem by the end of the weekend.

I need help. I will hire you to help me resolve this problem. I need someone who knows their VoIP and FreePBX $hl&. I know there is something I’m missing, but I just don’t know what.

Let’s get this one knocked out!

More than likely, your Internet Connection is not up to par. That’s where I’d start. You didn’t mention the speed of your internet connection, but that’s a likely place to start. What else is the internet connection? What was going on elsewhere on the network when the dropouts occur.


We’ve been having Comcast issues in the past, but I had a tech out a few days ago and he showed me their log with graphs including signal strength, speeds, etc. The modem hasn’t been down once in 2 weeks according to them.
We have business class internet with sustained download speeds of 20-30Mbps almost always and 2-3Mbps upload. On occasion we get choppy rdp sessions and we have choppy voice quality that usually correlates, but nothing showing signal loss.

I ran a ping capture for 3 days straight. We had 30 packets total lost over those three days, 1 of which was a full blown work day, 5 people in the office. pings averaged at 91ms with an occasional ping in the mix over 1000ms… but going through the capture file, that may have shown up once or twice in those 3 days.

I can’t definitively point the finger at the ISP (Comcast) because I have no way of proving it. I’ve sent PCAP files to the VoIP provider and they explained to me that my PBX was sending normal hangup requests, but the callers on both end of the phone would deny they hung up. No one is hanging up, but either the PBX is sending a goodbye, the service provider is dropping a packet that convinces the PBX that the call has dropped or I’m loosing my mind.

Comcast is the only ISP that comes to this location and at T1 would cost +$500/month (absurdly expensive and would rule out the value of VoIP)

I don’t have the tools or the skill to figure out why this is happening.


I need to know why I’m getting dropped calls. I need a plan to determine exactly why.
Is there an expert out there that can help me?

You most likely have a problem with your firewall.

I’m on my 3rd Firewall. I’ve changed to a Peplink Balance 30, port forwarding policies are set to allow 5060 and 10000-20000 through, services work. I’ve worked with PepLink directly to confirm that VoIP traffic is prioritized and confirm the router is in VoIP compatibility mode.

3rd router…

Just wondering if you ever found an answer on this? I have the exact same issue. I have three boxes deployed with the same configs and only one box is giving me grief.

Let me know.

You need to use real tools that analyze UDP packets. Ping Plotter Pro works but the Paessler VoIP module has a sender and a responder and works better. I am trying to find a Linux based tool that I can run a Raspberry Pi as the responder.

QoS on an Internet circuit is not truly possible. You can rate limit your outbound traffic but you can’t do anything about traffic inbound. If you have a mail server or other devices that receive large (especially autonomous) files/streams then you will most likely have congestion on the RX side of your Internet connection.

Broadband is so cheap I always suggest a dedicated connection for VoIP and then use the Internet as a backup.