What is Internet SIP Trunk?
Learn what Internet SIP Trunk is, what you can do with it, and when to choose Internet SIP Trunk versus Power Trunk.
Written by B3Networks Academy
Updated at November 12th, 2026
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Internet SIP Trunk is a high-capacity voice service that connects your PSTN and mobile phone numbers directly to your IP-PBX or Session Border Controller (SBC) over the internet, with support for High Availability, Geo-Redundancy, manual inbound failover, and call rules.
What you can do with Internet SIP Trunk
| Capability | What it does | Learn more |
|---|---|---|
| Connect your IP-PBX or SBC | Authenticate your PBX using a SIP Account (username and password) or static IP Peer, allow up to 2 public IPv4 addresses, and download your TLS certificate and firewall settings. | Set up authentication, HA, and number rerouting |
| Enable High Availability & Geo-Redundancy | Protect your voice traffic with Load Balancing, Auto Fail-over (2.5-second switchover), multi-zone High Availability Plus (2T), or multi-region Geo-Redundancy (4T). |
Set up authentication, HA, and number rerouting |
| Reroute incoming calls during maintenance | Turn on Reroute Inbound Call to forward incoming calls directly to a backup phone number without checking whether your PBX is online. | Set up authentication, HA, and number rerouting |
| Format numbers & restrict international dialing | Create Inbound and Outbound dial-plan rules (with a live preview tester) and manage your outbound Country Whitelist. | Manage Call Rules, Country Whitelist & Admins |
Explore the Internet SIP Trunk interface
When you open SIP Trunk in the portal, all settings are organized into four collapsible sections on a single page (SIP, Number, Call rules, and Admin):
Internet SIP Trunk vs. Power Trunk: Which one do I need?
Choose Internet SIP Trunk if you only need direct SIP connectivity for an existing PBX. Choose Power Trunk if you want to connect cloud calling apps, AI voice agents, or compliance call recording:
| Feature | Internet SIP Trunk | Power Trunk |
|---|---|---|
Direct SIP PBX / SBC Connectivity (Account or IP Peer) |
Yes | Yes |
Max 2 Single Public IPv4 Allowlist (/32) |
Yes | Yes |
| Inbound / Outbound Call Rules & Manual Fail-over | Yes | Yes |
High Availability (Load Balancing / Auto Fail-over), HA Plus (2T), & Geo-Redundancy (4T) |
Yes | Built-in 2-zone (Zone A / Zone B) HA |
Wholesale Token Number Sharing (Access Token) |
Yes | Yes |
Third-Party Cloud Calling Apps (MS Teams, Zoom, Webex) |
No | Yes |
AI Voice Agent (AgentDuet) |
No | Yes |
Call Recording (B3 Own Recording / SIPREC) |
No | Yes |