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SIP and DID: how the trunk and the number work together
Updated on 22 September 2026 in Guide
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The number is the public destination
A DID gives callers a number that routes to a configured destination. The number's country, type and registration requirements determine where it can be offered and how it may be used. Owning or renting a number does not define your phone system, simultaneous call capacity or outbound permissions. Confirm those separately.
The trunk connects the phone system
A SIP trunk links a compatible PBX to a provider's telephone network. SIP is the signaling protocol used to establish, manage and end the call; the audio travels as a separate media stream. A number may instead be delivered through a hosted phone service or forwarding, so a business does not always need to manage its own trunk. The number and the connection should be specified as distinct parts of the service.
Check what forwarding includes
Forwarding a business number to a mobile may suit a small team or a temporary migration. Before relying on it, check destination charges, concurrent call limits and what caller information reaches the recipient. Outbound caller ID, recording, queues and reporting need their own confirmation. They do not follow automatically from having an incoming number.
Prepare one brief for both services
Tell Neofone which countries and number types you need, which PBX you use, your expected simultaneous calls and how incoming and outgoing calls should work. Number availability and documentation are confirmed per destination. The connection can then be scoped for your existing PBX, Cloud Voice or agreed temporary forwarding. Include caller ID, fallback routing, responsibilities and acceptance tests in the agreed setup.