VICIdial Dial Prefix: Complete Optimization Guide

Quick Reference

Setting Name

dial_prefix

Default Value

9

Recommended

Varies by PBX config — often 9 or blank

Impact Level

Medium

Location in VICIdial

Admin > Campaigns > [Campaign] > Dial Settings

What Dial Prefix Does

A prefix added to the beginning of every outbound dial string before it is passed to Asterisk. Commonly used when calls must pass through an external PBX that requires an outside line access code (e.g., 9) before PSTN numbers. Must match your dialplan configuration.

Center Size Recommended Value Notes
10–25 Agents Varies by PBX config — often 9 or blank Start conservative, monitor for 48 hours before adjusting
25–100 Agents Varies by PBX config — often 9 or blank Scale gradually — larger operations amplify effects of misconfiguration
100–500 Agents Varies by PBX config — often 9 or blank Consult ViciStack optimization team for enterprise-scale tuning

How to Change This Setting

  1. 1 Go to Admin > Campaigns
  2. 2 Select campaign
  3. 3 Find Dial Prefix field
  4. 4 Enter the required prefix or leave blank for direct SIP dialing
  5. 5 Test with a known-good number after changes
  6. 6 Verify Asterisk dialplan matches expected dial string format
  7. 7 Submit

Common Problems

Double-dialing prefix when both campaign and dialplan add the prefix

Using wrong prefix causes all outbound calls to fail silently

Prefix not needed for direct SIP trunk configurations

filter_clean_cid_number Filter Clean CID Number Campaign force_dial_prefix Force Dial Prefix Campaign omit_phone_code Omit Phone Code Campaign outbound_cid Outbound Caller ID Campaign

ViciStack Module

How ViciStack Optimizes Dial Prefix

ViciStack's Dialer Tuning & Auto-Configuration module automatically monitors and optimizes dial_prefix based on real-time performance data from your operation. Instead of manual tuning, ViciStack continuously analyzes call outcomes, agent performance, and contact rates to recommend and implement optimal values — often catching configuration drift before it affects your numbers.

Learn About Dialer Tuning & Auto-Configuration →

Frequently Asked Questions

What does dial_prefix do in VICIdial? +
A prefix added to the beginning of every outbound dial string before it is passed to Asterisk. Commonly used when calls must pass through an external PBX that requires an outside line access code (e.g., 9) before PSTN numbers. Must match your dialplan configuration.
What is the recommended value for dial_prefix? +
The recommended range for dial_prefix is Varies by PBX config — often 9 or blank. The out-of-box default is 9. Note that optimal values vary by operation size, campaign type, and carrier — use ViciStack's automated tuning to find your exact optimal configuration.
Can ViciStack automatically optimize dial_prefix for me? +
Yes. ViciStack's Dialer Tuning & Auto-Configuration module monitors dial_prefix continuously and alerts you when the value drifts outside optimal range. On qualifying plans, ViciStack can automatically adjust this setting based on real-time performance data — no manual intervention required.

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