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Mix of 4 digit and 7 digit DN on CUCM and CUC

hello all,

We have a CM 9.1 cluster and Unity Connection 9.1.  We have multiple sites and deployed with 4 digit extension using the last 4 digit of DID.  e.g.  XXX-289-5220 becomes 5220 for the user's phone and unity voicemail.

Each site have their own PT and CSS in Call Manager and Unity Connection but there is only 1 phone system integration with the Unity Connection.

We have been lucky and not yet have overlapping extension in Unity Connection.

To avoid overlapping, we are considering deploying new sites with 7 digit extension. e.g.  XXX-289-6270 becomes 2896270 for the phone extension

This would give us a mix of 4 digit and 7 digit extension on the Unity Connection.
Anyone have experience with this type of setup?
If not, would anyone see what kind of issue this would cause?

thanks in advance,

Hall of Fame Super Silver

This is not a good design,

This is not a good design, and over the years i have remediated quite a few deployments where it was setup this way due to many reasons, mainly sooner or later you will run into overlaps and managing it via CSS/PT is one thing, UCNX is another, and more importantly there are applications such as CTI/JTAPI based applications (UCCX, UCCE, CER, CUEAC, etc) which are not partition aware and don't work well with it.

My suggestion would be to change it to either +e164 dial plan, uniform dial plan (i.e. 7 digits) or variable length flat dial plan (X digits between sites, 4 digits within a site) where the defined DN is the full X digits long and all DNs are in a common partition. 



Although it not being an

Although it not being an ideal design. To prevent overlap in CUC at least, expand the 4 and 7 digit DNs to full E164 or unique national numbers, using voicemail masks in CUCM.

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