Skip to content

Outbound Calls Fail

Symptom: dialing out from any extension produces "all circuits busy," "your call cannot be completed," fast-busy, or silent failure. Inbound calls work fine.

Most Likely Causes

  1. Trunk down — registration failed or IP-auth not working, no path out.
  2. No matching outbound route — the dialed pattern doesn't match any route's pattern.
  3. Outbound route trunk sequence empty or misconfigured.
  4. Carrier rejecting — auth issue, fraud-block, exceeded channel cap, account suspended.
  5. Class of Service blocking — extension restricted from this route.
  6. Firewall blocking outbound SIP/RTP to carrier.
  7. DNS failure — trunk hostname doesn't resolve.

Diagnose

# Step 1 — is the trunk online?
asterisk -rx "pjsip show registrations"
asterisk -rx "pjsip show endpoints" | grep -E "trunk|<carrier>"

# Step 2 — replicate the failed call and watch:
asterisk -rvvvvv
# Have the user dial. Watch for:
#  - Which outbound route matched ("Routing Pattern" line)
#  - Which trunk was tried
#  - The SIP response from the carrier (4xx, 5xx, 6xx)

# Step 3 — alternate: live SIP capture:
sngrep -d any host <carrier-ip>

Fix

Match the cause:

  • Trunk down: see Phone Won't Register — same diagnostic flow but for the trunk side.
  • No matching route: Trunk Attributes → Outbound Routes → check Dial Patterns. Test with one specific number known to be in scope.
  • Trunk sequence empty: open the route → Trunk Sequence for Matched Routes tab → ensure trunk is listed. Save → Apply Config.
  • Carrier rejection: the SIP response code tells you. 403 Forbidden = auth/account; 503 Service Unavailable = carrier overloaded; 404 Not Found = wrong destination format.
  • COS: User Attributes → Class of Service — verify the user's COS allows this route.
  • Firewall: verify outbound to the carrier's IPs/ports isn't blocked.
  • DNS: dig <carrier-fqdn> from the host. If it fails, fix DNS in System Admin → Sysadmin → Network Settings.

When to Escalate

Carrier returns weird codes (e.g. SIP 488 Not Acceptable Here consistently) or the same call works from another PBX. Open a ticket with the carrier, attach pcaps from sngrep -O <file>.