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ghost call but not from robots

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nitrox

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Hi,

one customer told me that sometimes some extension start to ring without anyone inside the office call them. For example extension 201 (snom 715 firmware 8.9.3.96 and android app 15.5.344.492) are leaved on the desk. The person which is using the extension 201 go to the office of extension 202 which is two rooms closer to the office of 201 and the extension 202 start to ring with caller that is 201. No one is trying to call 202 and the person which has the ability to call is not with the phone in front of him. No one is touching the keyboard of extension 201.

It is not a problem of some internet robots that are trying to call directly the phone because all the extension are behind an SBC and i have forwarded just the port 5090 and filtered it via an ACL inside the router. I have tried to call from an external network the port 5090 (just to see if the ACL is not applied and everything is working as expected).

I have filtered via iptables the ports 5060 tcp/udp and the port 5061 on the PBX as well, which is in our private cloud, I am not using SIPs but i have filtered it just to be paranoid. I have tested if the firewall is working and i cannot call the pbx outside the network which are specified on the configuration.

If i try to search the call to extension 202 i don’t see it in the call log. It is like the call is coming from the outside (robots or something like that) but everything it is filtered so i really don’t understand where the call are coming from. I have triple check my configuration and i asked to one colleague of mine to check if something is open from the outside and he confirmed that everything it is filtered.

What i don’t know is, when the phone start to ring, if it is ringing on the smartphone and the snom or just the snom. I am waiting to see if tomorrow it will happen again so probably i can tell you more.

This problem it is happening everyday 5 or 6 times. The extensions are randomly ringing and randomly calling so it is not something related to one specific extension.

In the begging i thought it was like a joke are someone was doing something wrong but now i think it is not a problem of the customer but it is something related to the pbx or SBC.

Any of you has discovered this issue?

thanks for the help in advanced.


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PBX virtual machine with 32 GB of hard disk/ 2 GB RAM/ 1 CPU (half of the ram is always free and the cpu is always under 10%)

SBC Intel core i3 with 4 GB ram and 40 GB of solid state hard disk.

45 extensions with mixed phones like snom 715 firmware 8.9.3.96/ snom d785 firmware 10.1.27.1 / smartphone android 15.5.344.492 / smartphone iPhone 6s 15.5.17.418 / Windows app 15.5.12227.5 / WebRTC(beta) enabled

Debian 9 iso from 3CX 15.5 SP6 PRO 16SC
 
Hi Paolo
"If i try to search the call to extension 202 i don’t see it in the call log."
In this case, try to enable SIP logs of 202 clients (the snom or android) and have a look at the incoming SIP INVITE there, see if you get a (useful) hint.
 
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