Set up Authentication, High Availability, and Number Rerouting in Internet SIP Trunk

Step-by-step guide to configuring the SIP and Number sections in Internet SIP Trunk, including Account, IP Peer, Access Token, High Availability modes, and Manual Fail-over.

Written by B3Networks Academy

Updated at November 12th, 2026

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Use the SIP and Number sections in Internet SIP Trunk to connect your IP-PBX or SBC, configure High Availability, download certificates and firewall specs, and set up manual inbound call rerouting.

Prerequisites

Make sure your organization has an active SIP Trunk base subscription, Concurrent Call license, and assigned phone numbers. Optional features such as IP Peer authentication and High Availability require their corresponding add-on licenses (see Internet SIP Trunk licenses and limits).

Configure the SIP section (Authentication & Downloads)

Expand the SIP section at the top of your trunk page to view your SIP Server hostname (such as sipsg02.b3networks.com), Location, proxy Domain IPs, and SIP Account Label (for example, SIP account 1).

Choose an authentication method

Select how your PBX or SBC connects to the trunk:

Method	License requirement	How to configure
Account (SIP Register — Username & Password)	Included in SIP Trunk Base license	1. Copy the SIP Username and select Reset password if you need a new password. 2. Select your Transport protocol (`TLS`, `TCP`, or `UDP`). 3. Under IP access allowlist, add up to 2 single public IPv4 addresses (CIDR subnets, IPv6, and hostnames are not accepted). 4. Configure your PBX/SBC to register to the SIP Server (registration timer: `3600s`).
IP Peer (Static IP)	Requires active IP Authentication Mode add-on on this trunk (tab is hidden when inactive)	1. Select IP Peer. 2. Enter your PBX/SBC IP address, Port, and Transport protocol for each applicable region/zone. 3. Select Save. (Note: The same IP Peer address cannot be shared across multiple active SIP accounts on the same domain; switching back from `IP Peer` to `Account` automatically clears the old IP peer entry.)
Access Token (Number Sharing)	Available on Primary accounts only (hidden on Secondary HA accounts)	1. Select Access Token when sharing this trunk's phone numbers to a receiving organization in Telco Hub / Number Management. 2. Because switching from `Account` to `Access Token` permanently disables the SIP account and revokes existing SIP credentials, type `CONFIRM` in the warning dialog to generate the one-time token.

Download TLS Certificate, SIP details, and Firewall details

At the bottom of the SIP section, use the three Download buttons:

TLS Certificate: Downloads the .pem certificate so your PBX/SBC can trust the SIP server over TLS 1.2+.
SIP details: Downloads audio codec (G.711 A-law, G.711 U-law, Opus), DTMF (RFC 2833), and signaling specifications.
Firewall details: Downloads the regional SIP signaling IPs/ports and RTP audio port ranges (10000–30000) to allow on your firewall.

Configure High Availability (HA)

If your trunk has a High Availability add-on license assigned, you can configure automatic failover in the SIP section:

Standard High Availability (`High Availability` add-on)

Creates a Primary and Secondary SIP account that share your trunk's Concurrent Call pool. Use the Account Switcher (Viewing: Primary | Secondary) to view each account, and choose a Routing Mode:

Only primary: Routes all incoming calls to the Primary SIP account only.
Load Balancing: Distributes incoming calls evenly (round-robin) across the Primary and Secondary SIP accounts.
Auto Fail-over: Routes calls to the Primary SIP account and switches to the Secondary SIP account within 2.5 seconds if the Primary is unreachable, unregistered, or fails authentication.

Advanced High Availability (`High Availability Plus` & `Geo-Redundancy`)

High Availability Plus (2T): 1 region with 2 zones (distributes traffic across both zones with 2.5-second failover).
Geo-Redundancy (4T): 2 regions (Primary + Secondary region) with 1 zone each (routes to the Primary region and fails over to the Secondary region).
High Availability Plus + Geo-Redundancy (2T + 4T): 2 regions with 2 zones each (fails over between zones in the Primary region first, then to the Secondary region if both primary zones are unreachable).

Configure Numbers and Manual Inbound Reroute

Expand the Number section to manage your trunk's phone numbers, outbound Caller ID defaults, and manual backup forwarding:

Main Trunk Number & Default callerID:

Main Trunk Number: Used as your fallback outbound Caller ID whenever your PBX sends a Caller ID that does not belong to your organization (default: Private).
Default callerID: Sets the outgoing Caller ID when a specific number is not sent by the PBX.

Reroute Inbound Call (Manual Fail-over — Free):

Switch Reroute Inbound Call On to immediately forward all incoming calls to an external backup phone number (such as a mobile phone or backup office) without checking whether your PBX is online.
In the Reroute table (Phone number → Reroute to), select Add to set individual backup numbers for specific DIDs.

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