Extension Numbering & Reserved Number Space

Scope

Intended Audience: All Users

This article outlines the reserved and permitted numbering schemes to use for extensions and features.

Restricted Numbering

This table outlines numbering schemes that may only be used for their designated purpose. Extensions created outside of the specified purpose will not work.

Extension Range	Designated Purpose
0 - 99	Reserved for internal use
211	FCC standard for community support information (free and confidential services) in some regions of the United States
311	FCC standard for municipal government services (non-emergency line) in some regions of the United States
411	Local Directory Assistance
511	FCC standard to access traveler information services in some regions of Canada and the United States
611	Customer Service
711	FCC requirement to connect a deaf caller to a Telephone Relay Service
811	Call Before You Dig
911	Emergency Services
933	Emergency Testing
988	National Suicide Hotline
700 - 719	Call Parking without Ringback
720 - 799	Call Parking with Ringback
5000	Unregistered Login to Voicemail - Prompts for extension and password
5001	Registered Login to Voicemail - Prompts for password only
9900	Unregistered Login to Voicemail - Prompts for extension and password
9901	Registered Login to Voicemail - Prompts for password only
9902	Hot Desking Sign In
7000 - 7999	Transfer to Voicemail
9900 - 9999	Reserved for System Features

Recommended Numbering

This table shows the recommended numbering scheme for extensions. The numbering scheme here is for reference and normalization purposes only, and does not need to be followed.

Extension Range	Recommended Purpose
100 - 599	User Extensions
800 - 899	User Extensions
1000 - 4999	User Extensions
5003 - 6999	User Extensions
8000 - 8999	User Extensions
9000 - 9099	Auto Attendants
9100 - 9199	Call Queues (Excluding Call Parks)
9200 - 9299	Special Extensions such as Forwarding Users, Call Routing Users, Analog/Paging Systems, & Fax Users