Reserved Extensions
Extension | Reserved Purpose |
00 – 99 | Internal Use |
411 | Local Directory Assistance |
611 | Customer Service |
811 | Call Before You Dig |
911 | Emergency |
933 | Emergency Testing |
988 | National Suicide Hotline |
700 – 799 | Call Parking |
900 – 999 | Internal Use |
5000 / 9900 | Unregistered Login to Voicemail (prompted for acct # and password) |
5001 / 9901 | Registered Login to Voicemail (prompted for password only) |
5002 / 9902 | Hot Desking Sign In |
7000 – 7999 | Unusable due to 7+extension rule to transfer a call directly to voicemail |
9900 – 9999 | System Features |
Best Practice
Extension | Usage |
100 – 599 | User Extensions |
700 – 719 | Call Parks – No Ringback |
720 – 799 | Call Parks – With Ringback |
800 – 899 | User Extensions |
1000 – 4999 | User Extensions |
5003 – 6999 | User Extensions |
8000 – 8999 | User Extensions |
9000 – 9899 | Special Extensions |
– 9000 – 9099 | Auto Attendants |
– 9100 – 9199 | Call Queues |
– 9200 – 9299 | Call Routing |
– 9300 – 9499 | Forwarding Extension |
– 9500 – 9599 | Virtual Extension |
– 9600 – 9899 | Future Use |