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Call routing to PSTN

Unanswered Question
Dec 20th, 2006
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I am trying to configure a IP Telephony Network with E1 PRI as MGCP Gateway to PSTN. We have DID enabled numbers, however few users who have the DID Numbers doesnt want their numbers to be directly displayed instead they would want the PRI Number to be displayed, is there a way to do this on the CCM?

Thanks & Regards,

Sriharshaa Prabhakar

Senior Network Engineer


Computer Network Systems

P.O. Box: 46144, Abu Dhabi, UAE

Tel :( +971-2) 6442888, Ext 2411

Mobile :( +971-50) 5212956

[email protected]

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Overall Rating: 5 (1 ratings)
ananddiwakar Wed, 12/20/2006 - 02:48
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Sriharsha, I do not know complete configuration of your CCM and gateways but can you just tru putting the Reception number or Pilot number in external phone number mask of that user's phone.

Sriharshaa Prabhakar Wed, 12/20/2006 - 06:06
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No, External Phone Number Mask is basically to display the number of the complete number on the IP Phone, however, this will not give the PRI Number when I call to the PSTN. I have already tried this....

sjhrhaskell Wed, 12/20/2006 - 06:23
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Hello Sriharshaa,

Actually, the External Phone Number mask SHOULD work for you. This is the only way to specify on a PER-USER basis what the calling party number is displayed as when the call goes out the gateway. Since the end users don't want their specifc number displayed, your mask will not contain any XXXX characters.

For example, let's say your user has an extension of 5555 and a DID of 555-555-5555 (Sorry, I don't know what numbering plan you're using, so this is NANP.) If you want the outside world to see 666-666-5555 instead, then the mask would be: 666666XXXX. If you want the outside world to see 555-555-5000, the mask would be: 5555555000.

In order for line-based External Phone Number Mask to work, there can be no Calling Party Transform Mask specified in any Route Lists that would be processed by the call. CPTM on a RL would take priority over line-based EPNM.

Also, you can watch what info is passing to/from the PSTN on an IOS gateway with the "debug isdn q931" command.

Good luck!


p.s. - What's the weather like over there today? It's -14C and sunny here.

Chris Deren Wed, 12/20/2006 - 06:25
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    2017 IP Telephony, Contact Center, Unified Communications

There are esentially 3 places you can conrtol the calling number number displayed on outbound calls with MGCP GWs.

1. The External Phone Number Mask on the phone

2. Calling Number TRansformation on Route Pattern, or if you want to use the External Number applied to the phone check the "use external phone number mask" checkbox here

3. Calling Number Transformation on Route Group from Route List configuration page

If you apply the transformation on Route Group it will override the one from route pattern, etc.

HTH, please rate all poats!


jbarcena Wed, 12/20/2006 - 07:22
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ll caller id configuration is made in the callmanager server.

In callmanager, caller ID for DID phone numbers and non-DID phone numbers are configured in the same way.

Please see below the places in callmanager administration where you can configure caller ID:


1) "Directory Number Configuration" page.

Scroll down to "External Phone Number Mask". Enter here the number that you want to send to the PSTN. Then click on "update" at the top of the page. You have to repeat this same procedure for the other extensions configured for this IP Phone (if you want to send those numbers also to the PSTN).


2) "Route Pattern Configuration" page.

Locate the route pattern that you are using for doing calls to the PSTN.

Scroll down to the "Calling Party Transformations" section.

- If you check the "Use Calling Party's External Phone Number Mask" checkbox, you will use the number that you configured in the "Directory Number Configuration" page as caller ID.

- If you uncheck that checkbox, then you can configure the "Calling Party Transform Mask". Just enter here a number like, as an example, 978858xxxx (callmanager will fill out the xxxx with phone's 4-digit extension).


3) "Route List Detail Configuration" page.

Go to the "Calling Party Transformations" section.

"Use Calling Party's External Phone Number Mask" > if you set it to "on", you will use the number that you configured in the "Directory Number Configuration" page as caller ID. If you set it to "off", then you need to configure the "Calling Party Transform Mask" (next line on this same page). The setting that you use here will override the settings that you configured in the "Route Pattern Configuration" page.

You configure the "Calling Party Transform Mask" here in the same way as explained for the "Route Pattern Configuration" page.


4) "Gateway Configuration" page.

Go to the Gateway and select the PRI that you are using for outgoing calls. Under 'Outbound Calls' you should see the Caller ID DN field. In here you can configure also the Caller ID.


In other words Caller ID works as follows:

- Gateway configuration overrides everything else.

- Route List configuration overrides the Route Pattern and the Directory Number Configuration.

- Route Pattern overrides only the Directory Number configuration.


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