Configuring Inter-Tenant Call Routing
This guide explains how to enable direct calling between tenants by using a second PortSIP PBX as an inter-tenant routing gateway.
This architecture allows users in different tenants on the same multi-tenant PortSIP PBX to call each other without routing calls through the PSTN.
Scenario
Assume that you already have PortSIP PBX A(Assume the IP address is 192.168.1.34) deployed and hosting multiple tenants.
You now want users in one tenant to call users in another tenant directly, without sending the calls through a PSTN provider.
To achieve this, deploy a second PortSIP PBX, referred to in this guide as PortSIP PBX B(Assume the IP address is 192.168.1.96). PBX B acts solely as a routing gateway between the tenants hosted on PBX A.
Example Tenant Numbering Plan
Assume the following DID ranges are assigned to tenants on PBX A:
Tenant 1
11000–11100
Tenant 2
22000–22100
In this example, a user in Tenant 1 can call a user in Tenant 2 by dialing the destination user's DID number, such as 22001.
The following diagram illustrates the overall deployment architecture and call-routing flow:
1. Configure PBX A
PBX A hosts the actual tenants, extensions, DID pools, and final inbound-routing rules.
1.1 Add PBX B as an IP Authentication Trunk
On PBX A, configure PBX B as an IP Authentication trunk.
This trunk is used to send inter-tenant calls from PBX A to PBX B for routing.
1.2 Allocate DID Numbers to the Tenants
On PBX A, assign the appropriate DID ranges to each tenant.
For example:
Tenant 1
11000–11100
Tenant 2
22000–22100
The following screenshot shows an example configuration:
1.3 Create an Outbound Rule in Tenant 1
In Tenant 1, create an outbound rule that routes calls destined for Tenant 2 through the PBX B trunk.
Example configuration:
Called number prefix
22
Route
PBX B trunk
With this rule, when a Tenant 1 user dials a number beginning with 22, such as 22001, PBX A sends the call to PBX B.
The following screenshot shows an example configuration:
1.4 Create an Inbound Rule in Tenant 2
In Tenant 2, create an inbound rule for calls received from the PBX B trunk.
Example configuration:
Trunk
PBX B trunk
DID number
22001
Destination
Extension 1001
With this rule, when PBX A receives a call from PBX B with the called number 22001, the Tenant 2 inbound rule routes the call to extension 1001.
The following screenshot shows the inbound rule configuration to route the DID 22001 to extension 1001 :
Set the route destination to extension 1001, as shown below:
2. Configure PBX B
PBX B acts as the inter-tenant routing gateway. It receives calls from PBX A and routes them back to PBX A, where the destination tenant's inbound rules perform the final routing decision.
2.1 Create a Single Tenant on PBX B
On PBX B, create a single tenant.
Set the tenant's SIP domain to the IP address of PBX B, as shown below:
2.2 Add PBX A as an IP Authentication Trunk
On PBX B, configure PBX A as an IP Authentication trunk.
This trunk is used to:
Receive calls from PBX A.
Route those calls back to PBX A for final tenant-level routing.
2.3 Allocate DID Numbers to the PBX A Trunk
Allocate a DID range to the PBX A trunk that covers all tenant DID numbers that may participate in inter-tenant calling.
In this example, use:
This range covers the DID pools assigned to Tenant 1 and Tenant 2, as shown below:
2.4 Create an Inbound Rule on PBX B
In the tenant on PBX B, create an inbound rule for calls received through the PBX A trunk.
Example configuration:
Trunk
PBX A trunk
DID number
11000–22100
Destination
0
This rule allows PBX B to accept calls from PBX A for DID numbers within the configured range and pass them to the outbound-routing process.
Configure the DID/DDI number as 11000–22100 . Refer to the following screenshot for the detailed configuration:
Set the destination number as 0, then the PBX will not modify the dialed number and just relay it. Refer to the following screenshot for the detailed configuration:
2.5 Create an Outbound Rule on PBX B
In the tenant on PBX B, create an outbound rule that sends calls back to PBX A.
Example configuration:
Called number prefix
0;1;2;3;4;5;6;7;8;9
Route
PBX A trunk
By matching all possible leading digits from 0 through 9, this rule allows PBX B to route any called number back to PBX A through the PBX A trunk, as shown below:
3. Example Call Flow
The following example demonstrates how a user in Tenant 1 calls a user in Tenant 2.
Example
A user in Tenant 1 on PBX A dials:
The call proceeds as follows:
The Tenant 1 outbound rule on PBX A matches the called-number prefix
22.PBX A sends the call to PBX B through the PBX B trunk.
PBX B receives the call from PBX A through the PBX A trunk.
PBX B matches the inbound rule for the DID range
11000–22100.PBX B applies its outbound rule and sends the call back to PBX A through the PBX A trunk.
PBX A receives the call from PBX B with the original called number
22001.Tenant 2 matches its inbound rule for DID
22001.PBX A routes the call to extension
1001in Tenant 2.Extension
1001rings and answers the call.
The call is now established between the Tenant 1 user and extension 1001 in Tenant 2 without using the PSTN.
The complete signaling path is:
4. Notes
For calls in the opposite direction, for example, from Tenant 2 to Tenant 1, create the corresponding outbound rule in Tenant 2 and inbound rule in Tenant 1.
Ensure that DID ranges assigned to different tenants do not overlap unless you have implemented a clearly defined access-code or routing-prefix scheme.
PBX B should be used only as the inter-tenant routing gateway in this architecture. The final destination-routing decision remains on PBX A and is determined by the inbound rules configured for each tenant.
This design keeps inter-tenant calls entirely within the PortSIP PBX environment and avoids routing them through the PSTN.
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