Adding prefix to outbound calls that pass thru CUCM

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Jan 26th, 2010
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CUCM 6.1.4 (with CER)

We've got an existing PBX who's calls flow through our CUCM to the PSTN (in and out).  Inbound from the PSTN is working just fine.  Outbound the PBX only pulses 4 digit extensions for the source (calling party); Which is great for us on the Cisco side for interoffice calls, not so much on calls directed to the PSTN. So many questions, not sure where to start...

-How can i prefix calls with only 4 digits to the PSTN with the full 10 digit for proper callerID when the PSTN gets the call?

We have about 3-4 number/prefix ranges (all 8xxx numbers get a (847)555- prefix while all 5xxx numbers get an (847)444- prefix) for our entire organization.  This means that 8123 may be on CUCM, 8122 may be on PBX. Which brings me to the next question...

-How can i keep this from affecting the existing CUCM calls going out the same gateway that do send the proper 10 digit callerID?

We're also using CER to modify 911 calls with new numbers for E911 that identify location and such.  These calls go out over the same gateways with the standard Cisco transformation patterns and such on the gateways.

-How do i keep it from messing with CER as well?


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Jaime Valencia Tue, 01/26/2010 - 19:30
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I assume you have some kind of trunk between CUCM and the PBX, the trunk will have an inbound CSS.

Create a route pattern for those calls which only that trunk can reach and prefix them there



if this helps, please rate

thanmad Wed, 01/27/2010 - 13:38
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So i would need two basic type of route patterns on the inbound of the pbx -> cucm?

Type 1 would look at calls from 1111 to 2222 and not tag them (basically a route pattern = xxxx set to "route this pattern")

Type 2 would look at calls from 1111 to 847-123-4567 and prefix them with 847-555-xxxx (847-555-1111) more of a route pattern that is RoutePattern = 9.@ set to "route this pattern" with "calling party transform mask: 847-555-xxxx"


if that's the case how do i accomidate for incoming 4digits calling ids that have different prefixs?  For example if the pbx sends two calls, one from 1111 which should be prefixed to 847-555-1111 and one from 3333 which should be prefixed to 847-444-3333.  i don't see a way to create a route pattern based on called number AND calling number.

Maybe i'm missing something


Jaime Valencia Wed, 01/27/2010 - 14:16
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Yeah you're right, this would not be able to do this for 2 sets of DID.

You should be able to do this with Calling Party Transformation Pattern but i can't recall if 6.X has this, i know 7.X does.

Jaime Valencia
PDI Engineer

thanmad Wed, 01/27/2010 - 14:52
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Ahhh, yeah, 6.x has calling party transformation patterns.

I can add those to partition on the gateway's css

pattern1 = 5xxx  "calling party transformation mask" = 847-333-xxxx

pattern2 = 4xxx  "calling party transformation mask" = 847-222-xxxx

but then is there a way to keep that from hosing my onsite calls?  the last thing i need is users hitting redial on their phones and using two trunk ports to hairpin back into the CUCM.

So that the above still works, but extension 1111 calling to 2222 still shows up as 1111?  Or will the transformation pattern apply to all calls and then i make a route pattern for internal calls that strips that all back out again (using a pre-dot option)?  that's assuming that the transformation pattern take place prior to the route patterns in the CSS...

or am i just confusing myself?


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