Extensions are the individual phone lines within your PBX system, and voicemail lets callers leave messages when an extension doesn't answer. This guide covers configuring both.
Creating an Extension in pjsip.conf
sudo nano /etc/asterisk/pjsip.conf[1001]
type=endpoint
context=internal
disallow=all
allow=ulaw
allow=alaw
auth=1001-auth
aors=1001
[1001-auth]
type=auth
auth_type=userpass
username=1001
password=CHANGE_ME_STRONG_PASSWORD
[1001]
type=aor
max_contacts=1This defines extension 1001 with a secure password — each additional extension follows the same pattern with a unique number and password.
Reloading Configuration
sudo asterisk -rx "pjsip reload"Configuring a SIP Phone or Softphone to Register
Enter the following in your SIP phone/softphone app:
Server: YOUR_SERVER_IP
Extension: 1001
Password: (as configured above)Setting Up Basic Dialplan for Internal Calling
sudo nano /etc/asterisk/extensions.conf[internal]
exten => 1001,1,Dial(PJSIP/1001,20)
exten => 1001,n,Voicemail(1001@default)
exten => 1002,1,Dial(PJSIP/1002,20)
exten => 1002,n,Voicemail(1002@default)Rings the extension for 20 seconds, then routes to voicemail if unanswered.
Configuring Voicemail Boxes
sudo nano /etc/asterisk/voicemail.conf[default]
1001 => 1234,John Doe,[email protected]
1002 => 5678,Jane Smith,[email protected]Format: mailbox => pin,name,email — the email address receives voicemail notifications if configured.
Enabling Voicemail-to-Email
[general]
[email protected]
attach=yes
format=wav49|gsm|wavattach=yes includes the actual voicemail audio file as an email attachment, letting users listen without dialing in.
Testing Voicemail
Call an extension that's set to not answer (or let it ring out), leave a test message, then dial into voicemail retrieval to confirm it was recorded correctly.
Setting Up Voicemail Retrieval Access
exten => *97,1,VoicemailMain(${CALLERID(num)}@default)Dialing *97 from an extension lets the user check their own voicemail directly.
Common Errors
Extension registers but calls don't ring through — verify the dialplan context matches what's configured in the extension's pjsip.conf entry.
Voicemail-to-email doesn't send — verify Asterisk's outbound mail configuration (typically via the system's configured mail transfer agent) is working correctly; test with a simple command-line mail send first to isolate the issue.
Continue Reading
- How to Install Asterisk PBX on a VPS
- How to Set Up an IVR (Interactive Voice Response) Menu
- How to Secure a VoIP Server Against Toll Fraud
Browse more articles in VoIP & Communication Servers.
