How a CID looks like


First of all I’m a very noob in IPBX. Sorry if my question does not seem smart or my explanation are not that clear, I’m still learning.
I have install a FreePBX server with one trunk ( OVH provider)

I have an issue with the trunk billed by the provider. They billed me on a “per second” trunk which is not even configured on the IPBX. (but we effectively owned this trunk)

They are telling me the CID is the problem. I asked them what should it looks like but they did not answered me.

Can you tell me what it should lool like in a tcpdump capture?

Any help would be really appreciated.

Many thanksby advance for any help

It sounds like they want the Caller ID you set in your outbound calls to match whatever they have told you your Caller ID should match. That’s reasonable - lots of places use that to prevent CID spoofing.

In your CID field in your trunk, set it to


Where “WHATEVER” is the name they’ve identified with your account. The “<NUMBER>” should be the number they assigned to your account. Quotation Marks and the braces (<>) are required in almost all cases.

Now, just to make it harder:

  • They may or may not require a Country Code or “+” on the CID.
  • They may or may not required the CID Name to match exactly.
  • They should have told you exactly what the CID Number needs to look like in the contract when you established this account.

You need to check with your provider to get the exact requirements for your specific implementation.

One last wrinkle:

CID is what this information is called when it’s coming “out of band”. There is also something called “Direct In Dial” (DID), which is what your phone number is. Many people confuse these. Here’s the difference:

On an inbound (to you) call, DID is the number that was dialed to get to you. CID is the number of the person calling you. CID comes in two parts - the CID Name and CID Number. There is no DID Name (it is only a number).

On an outbound (from you) call, there is a Dialed Number (the number you are calling) and a CID (your Caller ID Information).

This can be confusing for new installers, since the meaning of CID is opposite depending on which way the call is going. Your outbound Caller ID matches your Inbound DID. Because of this, people often confuse the terms and use them interchangeably, which clearly doesn’t work.

First all, many thanks for your answers.

You confirm the things I thought I understood.
Then, I forgot to mention something (and I’m sorry about that), I have no issue when I use the trunk number as CID (configured in trunk settings)

My issue is with the extensions CIDs that are not showing on the called devices.

Once again, there are two parts to the CID - the name and the number.

Your provider (from the sound of it) doesn’t allow you to use any CID Number except the one for your main line. You’ll need to either negotiate that with your provider or find a provider that allows “foreign” CID Numbers.

Ok, thanks for your answer. I’ll check with them again.

One last thing.

Someone correct me if I’m wrong, but I think you can also use “Diversion” headers to set the call’s Caller ID information. This way, the call goes to your provider “correctly identified” and then, once there, the header gets transferred to the recipient as the actual CID and you’re all set.

This is kind of an advanced topic, and I don’t actually have any requirement to do this, so my experience comes exclusively from reading the forum. @Stewart1 or one of the other regulars that handles these kinds of setup issues will probably weigh in.

Regardless of the facility (or fallacy) of this, you need to get the provider happy by sending them what they need you to send to your outbound calls will work. After that, it’s just negotiation.

thanks for your contribution. Finally I’ll say goodbye to this provider. I’ve been able to set the Caller-ID, show them that everything was OK from my side, but they are still telling me the problem is coming from our IPBX. (I have tested with FreePBX and 3CX and result are the same).

That’s how low cost providers work.


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