Panasonic VOIP (TLS) random audio problems

[ReeXNeeX]

Hi there,
we are using a Panasonic NS500 PBX unit which is cable connected to our LAN, to manage phone calls. The NS500 is an hybrid system which manages analog-in phone calls and SIP/TLS calls between hardphones and softphones. SIP server is local.

While there are no issues at all when using hardphones, softphone to softphone calls are experiencing random issues (no audio). I would say that 30% softphone-to-softphone calls have (no) audio issue, and when this happens, users are required to dial again until the audio is working. Softphones are based on the official Panasonic iOS/Android app

We have been working closely with Panasonic which is asking us to double check settings on the router.

Scenario:

• Peplink Balance One using 5 WANs
  

  

• Core LAN + 4 VLANs - Hardphones and PBX are connected to VLAN 400
  

  

• Softphones are connected to the SIP server either through Staff VLAN, or through the Internet:
  

  
  
  
  

• VLAN 400 is outbound-forced to WAN 2 (required by Panasonic to use same WAN as the SIP server’s public IP address)
  

  

• SIP-ALG is disabled
  

  

• Application blocking setup as:
  

  

• required port mappings are apparently configured correctly (notice that RTP is forwarded to the DSP card, which uses a dedicated IP address 172.16.4.11)
  

  

• The softphone app, when locally connected in LAN, might attempt to connect to the PBX using the remote SIP server address, and to avoid this, as the Balance One Hairpinning/NAT Loopback cannot be excluded, a custom service forwarding is required
  

  

• Firewall rules
  

  

Any suggestion?

[MartinLangmaid]

You have this deny rule which doesn’t make immediate sense to me since you have soft VoIP clients on the staff vlan right?

[ReeXNeeX]

Hello Martin,
apparently connections are only originated by softphones vs the PBX VLAN, which is allowed. To be honest, push notifications, which are being used to “wake up” softphones from deep sleep are initiated by the PBX, but this happens through the Internet. It’s a rather complicated architecture which requires softphones to authenticate each time they’re being used:

BTW, with the firewall rules that I have published, most of the times the softphones audio will work as expected, and I have also created a ANY ANY ANY firewall rule to see if the firewall was interfering somehow.

Nevertheless, I have added a couple rules to allow PBX mac address and DSP mac address to communicate with any network.

[ReeXNeeX]

As a side note, no message was logged into the firewall log, just to confirm that (apparently) the issue is not in the firewall

[MartinLangmaid]

But the issue is intermittent yes? Has it happened since you added the allow rules?

[ReeXNeeX]

Yes it does happen. I am now testing the softphones to be connected in the same VLAN as the PBX, however the issue keeps happening randomly

[MartinLangmaid]

Then you’ll need to run a network capture and make a bunch of test calls till it happens then review the VoIP traffic in the capture to see what is going wrong.

[ReeXNeeX]

Yeah, I’am doing so, but I it’s difficult to understand, using Wireshark, what is happening behind the scenes just looking at packets without knowing how the whole package is expected to work.
I will keep on investigating, thanks