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Wednesday, 21 August 2013

CUCM restrict caller ID ANI

"How to restrict or block a caller ID (ANI) from being sent, in CUCM" Or how to restrict Caller ID presentation"

Modification or restriction of ANI (Automatic number Identification, but I will use the term caller ID) is a very common requirement in Telephony deployments. There a heap of ways of modifying the caller ID and on CUCM deployments this is traditionally done through the external phone number mask on the extension, and then tick "use external phone number mask" on any particular route pattern, and even remove the external phone number mask altogether. And Robert's your father's brother! This method will not work however in conjunction with AAR. this is because AAR needs the external phone number mask combined with the AAR group prefix, in order to determine what number to reach an endpoint at when AAR is invoked.

Call Manager (yeah I know, old wording, but I just don't think it is very unified), version 8 brought with it, the wonderful world of Calling and Called party Transformation patterns (CngPTP and CdPTP). I have discussed the use of them in previous posts on Numbering plan normalisation . 

There are a few places, where CngPTP and CdPTP can be applied, namely:

  • On device pool level (under Device mobility Related Information)
  • On a Gateway Level (under Call Routing information - Outbound calls)

So these CngPTP and CdPTP patterns are NOT the same as the Calling Party Transformation mask that you would find under the Calling Party Transformations on a Route Pattern (again, these are the old world transformations).

Back to the original objective; blocking caller ID's. In order to block an ANI from being sent out, you would need to configure some sort of CngPTP.  Let us have a look at how such a CngPTP is configured and then focus on how to apply it.

Let take an example, of a phone with extension 57869, for which you want to restrict the ANI from being sent out, when making an external call.

This would require the following configuration:

Figure 1 - Calling Party Transformation Pattern Configuration
All that is required really is that the Calling ID presentation is set to Restricted .  

In the example above, I have created a dedicated partition called "CLI_Calling-P-T-Global-PT", in which I will place all the CngPTP's that require restriction.  In order to apply this transformation to outbound calls, I will add this Partition to a CSS called "CLI_Calling-P-T_Global_CSS" and use this on my outbound gateway (see below, Fig.2).

Figure 2 - Applying a Calling Party Transformation CSS to a gateway

If you want the caller ID presentation to only be blocked for external calls, you do not want to apply a CngPTP on a device pool level as this will also restrict calling ID presentation on internal calls. Which could be a requirement in a hotel for instance, where a receptionist might want to block her internal number presentation when calling guests.