No Sound On external SIP Asterisk

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.

1. 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.