It is recommended to use either 3 or 4 digit extensions. Results with 2 digits may be unpredictable.
With the exception of some specific numbers (eg 411,611) , the users and other items can be numbers almost anywhere, but for consistency, the following is recommended:
| 100 – 599 | Users extensions (Except 311,411) |
| 600 – 630 | Routing Users / Ring Groups / General Voice Mail etc
(Except for 611) |
| 631 – 650 | Conference Bridge extensions |
| 651 – 670 | Auto Attendants |
| 670- 699 | Call Queues |
| 701 – 729 | Fixed Space for Parking Functions
701-709: Can give option to leave a voicemail at timeout 710-719: No ringback 720-729: Ringback to park extension at timeout |
| 750 – 760 | Reserve for admin/office manager users requiring login only. |
| 800 – 899 | Users extensions |
| 1000-2999 | Users extensions (large companies only) |