Article ID:3873127

Extension Best Practices

Written By Jexter Reyes (Administrator)

Updated at July 8th, 2026

Objective

Customers usually have an extension scheme in place. When building out these extensions, we should strive to stick with the original scheme as much as possible. In the event we are starting from scratch, we should use this list as a base
 

Symptoms

  • What extensions can I use
  • What extensions are not available
     

Procedure

Users Extension Schemes

  • 100-999
  • 1000-8999
  • 10000-199999
  • 100000-199999
     

Extension Numbers Not Available for User Extensions

211 If you need assistance finding food, paying housing bills, or other essential services
311 Non-emergency phone number that people can call in many cities to find information about services, make complaints, or report problems like graffiti or road damage
411 Information
511 Local transportation and traffic information
611 Reserved for local telephone company repair
711 TTY
811 Call before you dig
833 Toll-free
911 Emergency
933 Used to test 911 location
988 Suicide hotline
5000  
5001  
9000-9999 Call Parks

TIP: Our preferences

ATAs and Faxes = 200+ or 2000+ (look up for exceptions). Set up as an Elite User.

 

EXAMPLE: To help with troubleshooting, an example setup for call flows would be the following:

For Call Queues, Auto Attendants, and Conference lines, build these on 8500-8999
For Call Parks, build these on 9000-9999
For Paging units (Snom, Cyberdata), 7777 and 8888 are the most common

 

 

Escalation Information

Escalation Information: SD1

If you need additional assistance, contact Crexendo Support at 855-211-2255 or email us at support@crexendo.com

 

Change Log

Date Description
Jul 9, 2026 Article created.