Trunks

Trunks let you connect your FlyNumber phone system to external VoIP providers for both incoming and outgoing calls. This gives you control over call routing, which providers handle your calls, and how caller information is displayed.

Enabled on request

The Trunks menu isn't shown on a new phone system. Contact FlyNumber support and we'll have it switched on for your account — activation happens on our side, so allow a little time. Once it's live, Trunks appears in the main menu with the three tabs described below.

Quick Start

Most users need trunks for one of these scenarios. Jump to the one that fits your needs:

I want to route all outbound calls through my own VoIP provider

Steps:

1. Go to Trunks > Termination Gateways and click +
2. Enter your provider's details (host, username, password, port)
3. Save the gateway
4. Go to Trunks > Termination Routes and click +
5. Create a route with:
   • Name: "All Outbound"
   • SRC Prefix: Leave empty
   • DST Prefix: Leave empty
   • Gateway: Select your new gateway
6. Save and test with a call

This catch-all route sends all outbound calls through your provider.

I want to route calls to specific countries through a different provider

Steps:

1. Create your termination gateway (if not already done)
2. Go to Trunks > Termination Routes and click +
3. Create a route with:
   • Name: "UK Calls" (or relevant country)
   • SRC Prefix: Leave empty
   • DST Prefix: "+44" (UK country code, adjust as needed)
   • Gateway: Select your gateway
4. Save and test with a call to that country

Calls to numbers starting with +44 will use your gateway; others use the default.

I want to receive calls from another VoIP provider on my FlyNumber system

Steps:

1. Go to Trunks > Inbound Trunks. A trunk named Default already exists; open it with Actions → Edit, or click + to create another
2. Copy the auto-generated Domain shown at the top of the General section (use the copy icon)
3. Add the external provider's number under Numbers > Phone Numbers so the phone system recognises calls to it
4. Configure your external provider to send calls to <number in E.164>@<trunk domain>
5. If your provider requires registration, enable it and enter credentials
6. Test by calling the number

Your FlyNumber system will receive calls sent to the trunk's domain.

---

Overview

The Trunks interface has three sections:

Section	Purpose
Inbound Trunks	Receive calls from external VoIP providers
Termination Gateways	Define connections to outbound VoIP providers
Termination Routes	Control which gateway handles which outbound calls

Why Use Custom Trunks?

• Cost Control: Route calls through cheaper providers for specific destinations
• Provider Flexibility: Use multiple VoIP providers at once
• Number Portability: Keep numbers with other providers while using FlyNumber features
• Redundancy: Set up backup call paths
• Custom Routing: Route based on caller ID, destination, or both

---

Inbound Trunks

Inbound trunks let you receive calls from external VoIP providers. Useful when you have phone numbers with other providers that you want to route through your FlyNumber system.

Creating an Inbound Trunk

1. Navigate to Trunks > Inbound Trunks
2. Click the + button
3. Configure settings:

Setting	Description
Domain	Auto-generated — copy it with the icon next to the field and give it to your provider. New trunks include the region you pick (see POP) in the domain
Friendly Name	Name shown in the list (e.g., "External Provider Trunk")
Transport Protocol	UDP, TCP or TLS
POP	Which of the two points of presence handles the trunk's calls: FRA (Frankfurt, default) or NYC (New York). Changing it changes the domain, so update your provider afterwards
Lookup destination by	How the called number is read from the incoming call: R-URI username part (typical) or To header username part
Allowed Codecs	OPUS, G722, PCMU, PCMA, G729, GSM, telephone-event — drag to set priority (left-most first). Keep telephone-event so key presses reach voice menus and feature codes

Numbers that reach you through an inbound trunk must also be added under Numbers > Phone Numbers — otherwise the phone system can't match the incoming call to a Phone Number module.

Registration (If Required)

Some providers require your trunk to register with them (registration is off by default):

1. Toggle Registration to ON
2. Enter:
   • Domain: Your provider's SIP registrar
   • Port: Usually 5060 — leave empty to use the provider's SRV or A record
   • Username and Password: From your provider
   • Contact User: Optional value for the Contact header

CLI Rules

Modify caller information as calls arrive:

• SRC number rule: a ready-made choice to Remove + or Add + on the caller's number
• SRC Name Rewrite Rule / Result: change caller names (e.g., add an "External: " prefix)
• DST Rewrite Rule / Result: reformat the called number (e.g., strip country codes)

The rewrite rules use POSIX Regular Expressions. See Understanding Regular Expressions below.

---

Termination Gateways

Termination gateways connect your system to external providers for outbound calls.

A FlyNumber-managed gateway is already there and carries your outbound calls by default; it shows a padlock and can't be edited or deleted. Add a gateway only when you want a third-party provider or custom routing.

Creating a Termination Gateway

1. Navigate to Trunks > Termination Gateways
2. Click the + button
3. Configure settings:

Setting	Description	Example
Name	Friendly name	"Main Provider"
Network Protocol	IPv4 Only (usual), IPv6 Only, Dualstack, IPv4 Preferred or IPv6 Preferred	IPv4 Only
Transport Protocol	UDP, TCP or TLS	UDP
Username	Auth username from provider	your_username
Password	Auth password from provider	•••••••
Host	Provider's SIP server	sip.provider.com
Port	Connection port (5060 if left empty)	5060 (UDP/TCP) or 5061 (TLS)
Allowed Codecs	OPUS, G722, PCMU, PCMA, G729, GSM, telephone-event — drag to set priority	OPUS, G722, PCMU

Codec Selection

• OPUS: Highest quality, more bandwidth
• G722: HD voice quality
• PCMU/PCMA: Standard quality, widely supported
• G729: Lower bandwidth, slightly lower quality
• Always include telephone-event for DTMF tones

CLI Rules for Gateways

Rule	Purpose
SRC Rewrite	Modify outbound caller ID
DST Rewrite	Reformat destination number

Useful for adding/removing country codes or presenting specific caller IDs.

---

Termination Routes

Routes determine which gateway handles each outbound call based on number patterns.

Key Point

Creating a gateway isn't enough—you must also create routes that tell the system when to use it. Without routes, calls use the default gateway.

Creating a Termination Route

1. Navigate to Trunks > Termination Routes
2. Click the + button
3. Configure settings:

Setting	Description
Name	Friendly name (e.g., "International Calls")
SRC Prefix	Match calls FROM numbers starting with this (optional)
DST Prefix	Match calls TO numbers starting with this (optional)
Gateway	Which gateway to use

Route Priority

When several routes could match a call, the one whose prefixes match most closely wins — a longer prefix beats a shorter one (+44207 beats +44, which beats an empty prefix). An empty SRC or DST prefix means "any". If no custom route matches, the call uses the FlyNumber-managed default gateway.

Common Route Configurations

Route all calls through custom gateway:

• SRC Prefix: (empty)
• DST Prefix: (empty)
• Gateway: Your custom gateway

Route UK calls through custom gateway:

• SRC Prefix: (empty)
• DST Prefix: +44
• Gateway: Your UK provider

Route calls from specific DID:

• SRC Prefix: +15551234567
• DST Prefix: (empty)
• Gateway: Your custom gateway

---

Troubleshooting

Problem	Likely Cause	Solution
Inbound calls never arrive	Number not added under Numbers > Phone Numbers, or provider sending to an old domain after a POP change	Add the number; re-copy the trunk domain and update the provider
Calls don't connect	Wrong gateway credentials	Verify username/password with provider
Registration fails	Network/firewall issue	Check connectivity to provider's server
One-way audio	Codec mismatch or firewall	Try different codecs; open RTP ports
Wrong caller ID	CLI rules needed	Add SRC Rewrite rule
Number format rejected	Provider expects different format	Add DST Rewrite to format numbers

---

Reference

Understanding Regular Expressions

CLI rules use POSIX Regular Expressions:

Pattern	Meaning
^	Start of string
$	End of string
.	Any character
\d	Any digit
*	Zero or more of previous
+	One or more of previous
()	Capture group
\1	First captured group (in replacement)

Example: Add "+1" to 10-digit US numbers:

• Pattern: ^(\d{10})$
• Replacement: +1\1

Inbound Trunk Use Cases

Use Case	Description
Multi-Provider Integration	Route numbers from various providers to one system
Legacy Migration	Gradually move from old phone systems
Geographic Presence	Maintain local numbers from different regions
Redundancy	Backup call paths for reliability

Outbound Route Use Cases

Use Case	How to Configure
Cost Savings	Route by destination country to cheapest providers
Quality Control	Premium gateway for important calls
Local Presence	Present local caller IDs per region
Failover	Multiple routes to different gateways

---

Getting Help

If you need assistance:

1. Open a support ticket with FlyNumber
2. Have your provider's documentation ready
3. Include (non-sensitive) details about your setup

tip

Some VoIP providers have specific FlyNumber integration guides—ask your provider if one is available.