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What is the DID Pool?

A DID Pool is a defined range of DID/DDI numbers associated with a specific SIP trunk in PortSIP PBX.

Because PortSIP PBX is a true multi-tenant platform designed for Cloud PBX and UCaaS service providers, multiple tenants may configure trunks from the same SIP trunk provider within a single PBX system.

Without proper isolation, this can lead to routing and caller ID conflicts, such as:

  • Multiple tenants configuring the same DID number in inbound rules, making it unclear which tenant should receive an incoming call.

  • A tenant using an outbound caller ID that belongs to another tenant, causing incorrect caller identification or call rejection by the trunk provider.

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Why DID Pool Is Required

To prevent these conflicts, PortSIP PBX introduces the DID Pool mechanism.

The DID Pool ensures that:

  • DID numbers are uniquely allocated per tenant

  • Inbound call routing is deterministic and unambiguous

  • Outbound caller IDs are restricted to authorized numbers only

This design is mandatory for large-scale, multi-tenant Cloud PBX and UCaaS environments.

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How DID Pools Work

Instead of adding DID numbers individually, the DID Pool allows you to define ranges of DID numbers for a SIP trunk.

Key capabilities include:

  • Adding large DID ranges efficiently

  • Splitting a range into subranges or individual numbers

  • Assigning ranges, subranges, or individual DIDs to specific tenants

Once assigned, a tenant can:

  • Configure inbound call routing rules

  • Set outbound caller IDs using only the DID numbers allocated to them from the DID Pool

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DID Pool Format

PortSIP PBX supports multiple formats for defining DID Pools. Multiple entries must be separated by a semicolon (;).

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Supported Formats

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Format Rules

  • A single DID number can be specified directly

  • A DID range is defined using a hyphen (-)

  • Multiple numbers or ranges must be separated by semicolons (;)

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Important Notes

  • Remove any leading +, 0, or 00 from DID numbers before entering them into the DID Pool.

  • Ensure DID ranges do not overlap across tenants to avoid routing conflicts.

  • DID Pool assignments are enforced at both inbound routing and outbound caller ID validation.

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Expected Outcome

With DID Pools correctly configured:

  • Incoming calls are routed to the correct tenant

  • Outbound calls use valid, tenant-owned caller IDs

  • The PBX operates safely and predictably in a multi-tenant cloud environment

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