Caller ID doesn't work at FXO port on Cisco Voice Gateway

This morning I participated in a discussion on Cisco Community about a problem with Caller ID on FXO port. And this discussion reminded me my recent experience with a similar problem, which one of my customer faced in his Cisco PSTN voice gateway. It was new configuration for a voice gateway in a small branch office. The symptoms of the issue were exactly the same - he couldn't see any Caller ID (Calling Number) on his Cisco IP phones, when the call arrived to FXO ports of the gateway (they used H323 signaling). However, when he connected a traditional analog phone to the PSTN line, the phone showed the Caller ID without any problems. It was new configuration for a voice gateway in a small branch office. 

The configuration of all FXO ports on my customer side were as follows:

voice-port 0/0/0
 supervisory disconnect dualtone mid-call
 supervisory answer dualtone
 no battery-reversal
 cptone CN
 timeouts call-disconnect 1
 timeouts wait-release 1
 connection plar opx 2100
 caller-id enable
 caller-id alerting line-reversal
 caller-id alerting dsp-pre-allocate

In the beginning of my VoIP career I dealt with the issues like that, so I already knew what to advise to my customer. The first thing to check in FXO port configuration is the cptone setting. Typically Cisco FXO port recognizes normally the Caller ID, if the cptone parameter is set to US. 

As you can see, my customer set the cptone to CN (I have no idea why they did it, because the customer was from Ukraine). Of course it was a wrong setting, and I advised him to substitute the cptone to US. Immediately after that on the next call they could see the desired Caller ID on Cisco phones.

Moreover, I should add that cptone US is a default Cisco configuration. However, sometimes the Caller ID is not shown for the calls on FXO ports, until you explicitly define it in the port config.

Is it tricky? Definitely yes. )))  

You can also find some more information about possible problems with Caller ID on FXO ports in this post on Cisco Community:

https://community.cisco.com/t5/ip-telephony-and-phones/fxo-interface-receive-calling-nuber-fail/td-p/2731202 

Have a nice weekend! Cheers!