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

[c449a766t]

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,

[Chris Deren]

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. 

HTH,

Chris

[Dennis Mink]

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.