Extension Numbering 4 or 5 digits - Cucm cluster

[J_Vansen_S]

hi All,

We are in the designing process of a new cucm UC infra setup.

We have 2 sites across town. Site A and Site B. We will be running 1 cucm per site and have them in a single cluster.

Total IP phones will be roughly 800-900.

What would be the best practice in terms of digit allocation?

Should we do

1. 5 digits, 2xxxx for both Site A and Site B as a whole
2. 4 digits, 2xxx for Site A, 3xxx for Site B

We will have 1 E1 link voice router per site.

Telco will be forwarding all DID and Numbering to both sites in parallel too.

Is there any pros and cons towards choosing one over the other?

If we choose 5 digits 2xxxx for both sites, will it be taxing on the intersite cluster WAN bandwidth?

Appreciate any advise

[Vivek Batra]

That depends on your future planning. Considering your current requirement, 4 digit numbering plan seems more than enough. Having different range for both sites like you mentioned will help you quickly identify whether extension belong to which site.

- Vivek

[Sreekanth Narayanan]

Scheme 2 would be better because it logically separates the extensions between the 2 sites. What's the bandwidth between the 2 sites? If the bandwidth is high enough, and depending on the maximum number of concurrent calls, there should be no issues with the Scheme 1.

But if you have Scheme 2, you could ask Telco to specifically route calls based on the DID dialed. 2xxx calls can come in on GW1 and 3xxx calls can come in on GW2.

[iptuser55]

to future proof yourself, dont do anything  other then E164 numbering as Directory numbers. Create DN`s as E164 with Plus and use Translations so to allow users to dial the end user by 4, 5 digits. In the future you may start to use Desk top dialling, Click to call etc and by setting your DN`s as E164 will save a lot of pain in the future