SIP Trunking Overview

SIP trunking on Cloud Voice connects your own PBX, SBC, or other SIP equipment to the public phone network. You create trunks in the dashboard, point your phone numbers at them for inbound calls, and place outbound calls through them with validated caller ID and STIR/SHAKEN signing. Everything on this page links into a deeper guide.

Trunk types

Cloud Voice supports three trunk types, distinguished by how they authenticate:

Type	Authentication	Best for
Register	SIP registration with auto-generated username and password	PBXs behind NAT or on dynamic IP addresses
IP	An allowlist of your IP addresses (CIDR notation)	Equipment with static public IPs
IP + Trunk Group	IP allowlist plus a trunk-group identifier	Multiple trunks sharing the same IP range

See Trunk Authentication for how each type works and when to choose which, and Create & Manage Trunks for the step-by-step setup.

Inbound: phone numbers (DIDs)

Each phone number on your account carries its own inbound routing. A number can:

• route to one of your trunks,
• route directly to a SIP URI or a domain,
• forward to another phone number, or
• stay outbound-only (inbound calls are rejected).

Details and when-to-use guidance are in Inbound Number Routing.

Outbound: caller ID and signing

Outbound calls through a trunk are validated before they reach the phone network:

• The caller ID you present must be a number authorized on the trunk, unauthorized caller IDs are overridden, never passed through. See Outbound Calling & Caller ID.
• International destinations are controlled per trunk with country-code allow and block lists.
• Calls are signed with STIR/SHAKEN attestation so they present trustworthy caller ID downstream.

Visibility and troubleshooting

Every call produces a call detail record, and each trunk exposes live registration status and call statistics, see CDRs & Call Troubleshooting. You can also receive push notifications for registration, call, and fax events via Webhooks & Events.

Beyond the basics

• Faxing over SIP, send and receive faxes on Cloud Voice.
• API Reference, programmatic access to trunks, stats, and fax.

New to Cloud Voice?

The fastest path: sign in at voice.izt.cloud, create a trunk under Infrastructure → Trunks, then assign a number to it from the Numbers page. The dashboard includes an interactive “Set Up a SIP Trunk” guide that walks you through it live.