3CX Version 20 SIP Trunk Configuration
Simtex SIP Trunks from $4.99/month
Business-grade SIP trunking with geo-redundant infrastructure, crystal-clear audio, and Australian-based support. Pay-as-you-go or unlimited plans available.
SIP Servers:
- West Coast (AU):
siptcp.simtex.com.au - East Coast (AU):
siptcpeast.simtex.com.au
Choose the server closest to your 3CX instance. Our platform publishes NAPTR and SRV records — 3CX's Auto Discovery feature will automatically resolve the correct connection details.
Do not expose your 3CX system on a public IP address unless you have appropriate security measures and firewall rules in place. For self-hosted deployments, ensure your SBC (Session Border Controller) or firewall is correctly configured before connecting to any SIP trunk provider.
Why Generic VOIP Provider (Registration)? Simtex uses registration-based authentication where your 3CX system registers with our servers using your account credentials. Do not select the IP-based option.
East Coast? Replace
siptcp.simtex.com.au with siptcpeast.simtex.com.au in the Registrar/Server field if your 3CX instance is located on the East Coast of Australia (NSW, VIC, QLD).If Auto Discovery doesn't work (trunk fails to register), uncheck Auto Discovery and set the port to
5062 with the transport set to TCP. Some network environments or DNS configurations can interfere with SRV resolution.G.711 A-Law is the standard codec for Australian PSTN interconnection. It provides toll-quality audio at 64kbps with no transcoding overhead. Always place it first in the priority list.
Catch-all route: Set up a default destination for unmatched DIDs. This ensures calls to numbers you haven't explicitly configured still reach someone — typically a receptionist or main ring group.
Recommended Outbound Rules for Australian Numbering
| Rule Name | Pattern / Prefix | Strip Digits | Prepend | Example |
|---|---|---|---|---|
| Local Calls | XXXXXXXX (8 digits) | 0 | — | 94883344 |
| National Calls | 0XXXXXXXXX (10 digits starting with 0) | 1 (strip leading 0) | — | 0894883344 → 894883344 |
| Mobile Calls | 04XXXXXXXX (10 digits starting with 04) | 1 (strip leading 0) | — | 0412345678 → 412345678 |
| Emergency | 000 | 0 | — | 000 |
| 1300/1800 | 1300XXXXXX or 1800XXXXXX | 0 | — | 1300888519 |
| 13 Numbers | 13XXXX (6 digits starting with 13) | 0 | — | 131313 |
| International | 0011X. (starts with 0011) | 0 | — | 001161894883344 |
International dialling: If you do not need to allow international calls, simply don't create the International outbound rule. This is the simplest way to prevent unauthorised international dialling and potential toll fraud.
Prefix for external calls: Consider requiring a prefix (e.g.
0) before external numbers. This prevents internal extension numbers from overlapping with external destinations and is standard practice in Australian PBX deployments.Toll fraud is real and expensive. An unsecured PBX can rack up thousands of dollars in fraudulent international calls within hours. Always limit SIM calls, disable international routing if not needed, and enable 3CX's built-in anti-fraud protections.
Trunk not registering? Check these common issues:
- Verify your account number (
214XXXXXXX) and password are correct — copy/paste to avoid typos - Ensure Auto Discovery is checked and the port shows
0 - If Auto Discovery fails, uncheck it and set port to
5062, transport to TCP - Check your firewall allows outbound TCP connections (port 5062 or the SRV-resolved port)
- If self-hosted, confirm your 3CX server can resolve
siptcp.simtex.com.auvia DNS - Try the alternate server (
siptcpeast/siptcp) in case of regional connectivity issues
Caller ID validation: Simtex validates outbound caller IDs against your account. Only DIDs allocated to your trunk will be transmitted — any other number will be replaced with your main trunk number automatically.
Last updated 26 March 2026