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Phone Numbers (DIDs)

In FS PBX, Phone Numbers usually refer to your external numbers from a carrier—often called DIDs. These are the numbers people dial from the public phone network to reach your business.

If you’re coming from Asterisk: this is the “inbound DID” side of your trunking setup.

What is a DID?​

A DID (Direct Inward Dialing) number is a public phone number like:

  • (555) 111-0000

When someone calls that number, the call comes from your carrier into FS PBX and must be routed to something inside your Domain.

Phone Numbers vs Gateways (common confusion)​

These two work together, but they are not the same:

  • Gateway = the connection to your VoIP carrier (the “trunk”)
  • Phone Number (DID) = the number that arrives on that connection
  • Destination = where the call goes (extension, ring group, IVR, queue, etc.)

Simple flow:

Caller → Carrier → Gateway → FS PBX → DID match → Destination

Do I need Phone Numbers for internal calling?​

No. Internal extension-to-extension calling works without any DIDs.

You need Phone Numbers when you want:

  • inbound calls from the public network
  • “main line” numbers, direct lines, support lines, etc.

Where Phone Numbers live in a multi-tenant system (Domains)​

In FS PBX, Phone Numbers are typically assigned to a specific Domain so the system knows which tenant should receive the call.

This is what makes multi-tenancy work cleanly:

  • Company A can have its own DIDs and routing
  • Company B can have different DIDs and routing
  • Calls don’t “bleed” across tenants

What happens when a DID is called?​

Each Phone Number (DID) should be mapped to a Destination, such as:

  • Extension (direct line to a user)
  • Ring Group (hunt group / simultaneous ring)
  • IVR (auto-attendant: “Press 1 for Sales…”)
  • Queue (call center)
  • Call Flow / Time Conditions (day/night routing)
  • Voicemail (for departments or after hours)

So when you add a phone number, the most important step is: decide where it should go.

Outbound caller ID (why phone numbers matter for outbound too)​

Even though DIDs are mainly “inbound,” they often also determine what people see when you call out.

Common outbound setups:

  • Each extension presents its own DID as caller ID
  • Everyone presents the company main number
  • Different departments present different numbers (Sales vs Support)

This is usually configured via extension settings, outbound routes, and/or domain defaults—depending on your setup.

Typical setup workflow​

  1. Confirm your Gateway is working
  • registration trunk or IP-auth trunk
  • inbound calls are reaching your system
  1. Add your Phone Numbers (DIDs)
  • enter the DID in the correct format your system expects
  • assign it to the correct Domain
  1. Set the Destination Examples:
  • Main number → IVR
  • Sales number → Ring Group
  • Direct line → Extension 101
  1. Test inbound
  • call each DID externally
  • verify it hits the right destination and the right Domain
  1. Verify outbound caller ID
  • place outbound calls and confirm caller ID is correct

Common gotchas​

“Inbound calls hit the PBX but don’t go anywhere”​

Usually:

  • the DID isn’t added, or
  • the DID exists but has no destination, or
  • the DID format doesn’t match what the carrier sends

“My DID routes to the wrong tenant/domain”​

Usually:

  • the phone number is assigned to the wrong Domain, or
  • multiple rules match and a different one wins

“Caller ID looks wrong on outbound calls”​

Usually:

  • extension caller ID not set
  • outbound route overrides caller ID
  • carrier requires a specific caller ID format (often E.164)