If like us, you've spent months on Small Business IT Support, trying to find out why a perfectly installed FreePBX/Asterisk system will not work with an external SIP extension, then I really feel for you!
Asterisk is great "When It Works", but when it doesn't, You probably end up with many headaches and increased stress levels.
Well, today - FINALLY -
We fixed our issue with no sound on external sip calls and we're going to explain just how we did it.
If however, you'd like some help, we can fix your voip issues remotely. Just book an appointment and we'll assist.
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No sound with SIP | No Sound With Asterisk| No Sound With NAT
To correctly troubleshoot your issue, make sure that the following steps are taken.
- On your router, open up the following ports and forward them to your asterisk box. Your asterisk box may be in the form of (FreePBX, AsteriskNOW, or TrixBox)- They all use the same format
SIP One Way Audio Troubleshooting
Once these ports have been forwarded to the IP of your Asterisk server, give your router a reboot. Re-Login to your router just to reconfirm that the posts are in fact pointing to the correct IP of the Asterisk Server.
The next step is to ensure that you configure your NAT settings on the Asterisk server correctly.
The following image shows how best to set up your settings.
If you're behind a router with a Static IP but your internal network (including Asterisk) is on a 192.168.x.x network, these settings apply to you. If not, simply change these to work with your network setup.
Another important tip for troubleshooting your sound issue is to make sure that you enable the codecs that you will be using. If you're using a softphone, for example, make sure it supports calling with your enabled codecs. If not - Make sure you enable them in Asterisk. If they're not listed, try a different softphone but generally, you should be okay.
All the other configuration options are not external to Asterisk. This is where I went wrong. I tried tweaking and changing asterisk settings for months to no avail.
If you have No Audio - It's down to an incorrectly configured ROUTER or FIREWALL.
If you've configured the ports as I've shown above, there are only a few things left to check.
1. Internal firewall. If you're using a softphone on a machine, make sure the firewall is disabled for testing. If it works, you need to open up the same ports on the machine as you did in the router.
2. Router. Many of today's commercial routers implement SIP ALG (Application-level gateway), coming with this feature enabled by default. While ALG could help in solving NAT-related problems, the fact is that many routers' ALG implementations are wrong and break SIP.
THIS WAS WHAT WAS WRONG WITH OUR SETUP
Everything on my router was in fact correct. I had never heard of ALG before, mainly because there was no mention of it on my router admin panel anywhere. Even though ALG was not mentioned on my router page, it's still there and active, just not visible on the front end.
We had to telnet into my router and login and then issue a command to turn ALG off.
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List of routers with SIP ALG enabled
The following is a list containing SIP ALG router models, their issues, and how to disable SIP ALG (enabled by default in most of the cases). Please
add more data to this list if you have experimented problems due to a SIP ALG router.
SpeedTouch
Models:
ST530 v6 (firmware >= 5.4.0.13) comes with SIP ALG enabled by default.
NAT type: symmetrical
Issues:
- It replaces the private IP appearing in SIP headers with the public IP using a dumb text replacement. If for example, the private IP appears in the "Call-ID" it replaces it too (that it's completely unnecessary).
To disable SIP ALG:
~# telnet router
-> connection unbind application=SIP port=5060
-> saveall
Zyxel
Models:
660 family comes with SIP ALG enabled by default.
NAT type: symmetrical
Issues:
- SIP protocol is broken making 50% of outgoing calls impossible because the wrong values are inserted into SIP headers.
To disable SIP ALG:
~# telnet router
Menu option "24. System Maintenance".
Menu option "8. Command Interpreter Mode".
ip nat service sip active 0
Netgear
Models: WGR614v9 Wireless-G Router, DGN2000 Wireless-N ADSL2+ Modem Router
Firmware V1.0.18_8.0.9NA
To disable SIP ALG: From Wan Setup Menu, NAT Filtering, uncheck the box next to "Disable SIP ALG"
SMC
Models: ToDo
NAT type: No symmetrical
Issues:
- The ALG doesn't replace the private address in the "Call-ID" header (that is correct) but it does replace the "call-id" value in the "Refer-To" header so SIP transfer is broken.
To disable SIP ALG: ToDo no ALG related options found via web and telnet. No idea of how to disable it.
Linksys
Models: WRV200, WRT610N
NAT type: Symmetrical
Issues:
- The ALG replaces the private address in the "Call-ID" header (not needed at all). Some phones (as Linksys with the latest firmware) encode the "Call-ID" value in the "Refer-To" header (by escaping the dots) so the private IP appearing there is not replaced with the public IP. This causes that the call transfer fails since the proxy/PBX/endpoint will not recognise the dialog info.
To disable SIP ALG: ToDo no ALG related options found via web and telnet. No idea of how to disable it.
To disable SIP ALG on WRT610N: Web Interface: Administration, Management, under heading 'Advanced Features' SIP ALG, can be disabled.
Fortinet
Models:
800 comes with SIP ALG enabled by default.
To disable SIP ALG:
~# telnet firewall
config system settings
set sip-helper disable
set sip-nat-trace disable
endconfig system session-helperdelete 12
end
If you require some additional help with your VOIP system, why not try our
Remote IT Support service.
In Summary
If you're experiencing issues with not hearing anything on a SIP (Session Initiation Protocol) call, there can be various reasons for this problem. Here are some common troubleshooting steps to help you diagnose and potentially resolve the issue:
-
Check Your Audio Devices:
- Ensure that your microphone and speakers (or headphones) are connected and functioning properly.
- Make sure your audio devices are selected and configured correctly in the SIP client or softphone you are using.
-
Check Audio Settings:
- Within your SIP client or softphone, check the audio settings and make sure the correct audio input (microphone) and output (speakers/headphones) devices are selected.
-
Internet Connection:
- A poor or unstable internet connection can lead to audio issues on SIP calls. Check your network connection for stability and sufficient bandwidth.
-
Firewall and Port Configuration:
- Ensure that your firewall or network settings are not blocking the necessary ports for SIP traffic. SIP typically uses UDP and TCP ports 5060 and a range of UDP ports for media (e.g., 10,000-20,000). Verify that these ports are open.
-
NAT (Network Address Translation) Issues:
- If you're behind a NAT router, you may need to configure it to allow SIP traffic to pass through. Look into setting up port forwarding or configuring a STUN server in your SIP client.
-
Audio Codecs:
- Check if there are any compatibility issues with audio codecs. Ensure that both ends of the SIP call support the same audio codecs.
-
Firewall Rules and SIP ALG:
- Some routers have SIP Application Layer Gateways (ALG) that can interfere with SIP traffic. Try disabling SIP ALG in your router if it's causing issues.
-
SIP Server Configuration:
- Verify that the SIP server you are connecting to has the correct configuration for audio routing and media handling.
-
Test with Another Device:
- Try testing the SIP call with another device or SIP client to see if the problem is specific to your setup.
-
Update SIP Client:
- Ensure that you are using the latest version of your SIP client, as updates may include bug fixes and improvements.
-
Contact Your SIP Service Provider:
- If the issue persists, reach out to your SIP service or Business IT support provider for assistance. They may be able to diagnose and resolve the problem from their end.
By systematically checking these potential issues and making the necessary adjustments, you can increase the chances of resolving the problem and getting your SIP calls to work with proper audio.
If you need a little help troubleshooting your VOIP issues, book an appointment below
