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CLID restriction for


We have got a Cisco 2821 router on which Voice E1 PRI is terminated and is working fine.We have gor a DID facility with Toll free number and it is a Call Center setup.Toll free number is mapped to Pilot number.

Cisco 2821 is integrated to Call Manager version 7.1.5  on MGCP.We want that whenever any agent calls outside through PSTN -Voice PRI , the Pilot Number should not be displayed.It should display number of our choice so that nobody from outside can call to Pilot Number.

Only outside users can dial tollfree number.

Please advise.




CLID restriction for

This can be done in several places. Starting from the "outside-in":

1. Gateway. On the MGCP gateway, under "Call Routing Information - Outbound Calls" you can set the caller ID DN to a static number. This would apply to every call presented from the gateway to the carrier. If the PRI in question is only used for agents, then this would work. If you wanted to apply this masking to only a subset of egress calls, this option does not work.

A variation is to use the transformation pattern rules. Where you can provide a more granular/mature set of rules to a pattern and then apply a transform. Very handy and this may be one of the best options. Look into "Calling Party Transformation CSS" on gateways.

2. Route List/Route Group mapping. When you assign a route group to a route list you have the option to tinker with the Calling Party Transforms. Typically you use this method when you have some sort of calling party transform behavior you want to apply and you want a different behavior applied depending on target route group. For example, you have a route group that points to a carrier and another one that poitns to a PBX (a failover tandem point). To the carrier you may want to do something like strip a "9" but to the PBX you may want to keep the "9" intact. While you could use a similiar logic to deal with the source of your call, it isn't a logical fit and this approach probably isn't for you.

3. Route pattern. You can tweak calling party transforms at the route pattern level too. If your agents were hitting a route pattern that was dedicated to them then this approach is viable

4. Line level. You can use the External Mask setting on the directory number (assigned to an agent line) to mask the CLID. Just make sure that the previous levels are honoring the external mask. You can see the "Use calling external mask" option under route patterns,  route list/route group assignments, and calling party transformation rules.

There are many places to do this and you should also understand that there is a priority order here. If you were to modify the "caller ID DN" parameter at the gateway level, it will override any settings made on the route list, route pattern, or line level. Further, the route list/route group will override the transformations at the pattern level, and so on.

I usually set the external mask on the agent line to be the number I want presented and then ensure that the external mask on the directory number is being accepted at the route pattern, route list/route group level. I go this route because usually I assign a specific line that should only be used for call center calls. Agents may or may not have a personal line. I also use a private (or internal) number on that agent line. So, relying on external mask seems to be the path of least resistance. If I want/need something more "global" then I will use calling party transformation rules at the gatewya level. Again, this works for me because I make sure agent lines are in a contiguous and easily masked block of directory numbers.

So, configuring CUCM to mask your calls is the easy part. You have tons of options, totally achievable. The important question is: will your carrier accept calls where you are presenting your toll free number as the CLID? That is something you can test easily. If there is a problem (like your carrier rejecting the call or substituting what is known as the "bill to number" or BTN) then you have to have a chat with your carrier.




HTH -Bill (b) (t) @ucguerrilla

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CLID restriction for

Hi William ,

We have tried the first option but still when call is made from agent to PSTN, number displayed is Pilot Number.



Hall of Fame Super Red

CLID restriction for

Hey Bill,

I have bookmarked this great answer for future reference +5

Great stuff!



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