Solved Calls go silent after about 10 minutes

[RS-IT]

Hi All,

I am posting this here because I can't seem to figure this out. We are having an issue where someone will be on a call with someone external, and after around 10 minutes, the call goes silent on both ends. It remains connected, but neither side can hear each other. Reports of this happening have come from multiple different people here, including myself, so I don't think it's the phones. This issue seems to have started around the time we switched from our local SIP to Voxtelesys. This would lead me to believe it's something to do with that connection, but I'm not sure what it would be.

We are using the image 3cx publishes, and it is running v20.

Has anyone else had this issue, and if so, how did you fix it?

 

[Kevin@voxtelesys]

Resolution for any other customers with similar issues.

Voxtelesys enabled tracing on the customer account, RS-IT was able to make some test calls and see the SIP ladder of the call from our portal to see the firewall was changing the SIP port on the registration attempt, when Voxtelesys sent the ACK back to the 200ok to confirm the call setup the firewall blocked the request, 3CX eventually (30 seconds) disconnected the call. RS-IT was able to make some firewall changes and now the call setup is correct.

If any Voxtelesys customer have similar issues let us know and we can enable the same trace settings for trouble shooting, screenshots below are just an example of the portal call ladder. Under analysis we let you know if there are any issues and give hints on resolving.

 

[paulodagraca]

Hello Kevin,

Great work, you have 'support' on the right level.
Would be nice, if we could also have some information about the (Palo Alto) firewall change.

Paulo

 

[Kevin@voxtelesys]

Hello Kevin,

Great work, you have 'support' on the right level.
Would be nice, if we could also have some information about the (Palo Alto) firewall change.

Paulo

RS-IT would have to share those details as we just provided the tool to help troubleshoot and didn't make any changes to any equipment.

 

[paulodagraca]

Kevin,
Yes correct, understand that.
Paulo

 

[RS-IT]

Yes, was just going to share what I did.

First of all, we are still verifying that the silent calls issue is fixed, but so far so good.

Now for the changes:
1. Disable SIP ALG
-Go to Objects -> Applications
-Search for sip. Click it.
-By ALG, click Customize. Check the Disable ALG box.

2. The other part was NAT related. It appears that your default NAT rule that just translates all your traffic to and from your public IP address isn't good enough for Voxtelesys' ACK packet to make it back into the firewall and to the 3cx server. After 30 seconds, the 3cx server thinks the call never made it to Voxtelesys, even though it did, so it sends a BYE packed to end the call.

I setup a NAT rule that specifically translates SIP traffic from Voxtelesys' IP address ranges to our public IP address, and it forces it to be on port 5060. The rule below stops the calls from being dropped after 30 seconds.

 

[RS-IT]

I didn't know if Voxtelesys wanted their public IP address ranges out there, so I blanked it out. I got the range of addresses from Kevin at Voxtelesys though.

 

[RS-IT]

Oh also, you will need to allow SIP traffic from Voxtelesys to your public IP address as well in a separate policy rule. Otherwise, it will still be blocked.

 

[KyriacosS_3CX]

Thank you all for the detailed write down of the troubleshooting steps and steps taken to resolve.