Specifications

Dialing Plan
Planning and Installation Guide 6 – 11
dialing plan were complex and the complexity increased with the number of people
and extensions involved.
For example, if one company acquired another company and the two companies
wanted to merge their phone systems, then no two users could have the same user
extension, even if they were at different sites with different prefixes.
Users will be able to call other users within a site by dialing only the user number.
Inter-site calls would require users to dial the extension prefix plus the user number.
Off-system extensions (OSE's) will continue to be used to route calls to legacy PBX's.
How It Works
Figure 6-7 Abbreviated 4-digit dialing with extension prefix
As shown in the illustration above, On-Net Dialing assigns extension prefixes to each
site or to a group of sites. All calls are placed "on the network" if they are within the
same prefix, and the user need only dial the user extension. Calls preceded with the
trunk access code (usually "9") are sent to the PSTN.
Benefits of On-Net Dialing:
• Scalability – For larger organizations, On-Net Dialing enables the creation of a
common and consistent "cookie cutter" dialing plan that can be replicated
throughout an organization that has many offices. For example, a department
store might have a phone in each of its different departments with one for
clothing, furniture, kitchenware, etc. With On-Net Dialing, a user can assign the
extensions of 4000, 5000, 6000, and 7000 to each of these departments. By
modifying the 3-digit site code/extension prefix at each location, this approach of
assigning 4-digit extensions to departments can be replicated across an entire
department store, nationwide, so that a user who knows the extension for the
automotive department in one city could travel to another city and would know
how to reach the automotive department if he knew the site code.
• Preserve existing legacy dialing plans – As mentioned before, you can preserve the
existing dialing plans when adding ShoreTel equipment to a deployment with