Tech

Inter-Office Trunks

Published on:

June 21, 2013

Previous versions of the PBX allowed calls from one trunk to be routed through another for cost-effective call termination - this was commonly used by international offices. Now, the new inter-office trunk feature enhances this by assigning a dial plan directly to the trunk, offering greater flexibility in caller ID presentation. This allows businesses to optimize call routing without linking to specific extensions. While prepaid accounts aren’t supported, the feature enables broader applications, such as acting as a session border controller (SBC), handling LAN-WAN traffic, and translating calls between IPv4 and IPv6. Available from version 5.0.10i, this expands the role of the PBX in networked environments.

In previous versions of the PBX, there was already a setting, “assume the call comes from extension so-and-so”. This was a trick to make it possible for a call coming in on one trunk to end up on another trunk for outbound call termination.

The practical relevance for this was international offices could use this trick to locally terminate calls from their branch offices. For example, when a company had offices in Boston and Berlin, making a phone call in Germany from the Boston office could be done using the PBX in the Berlin office, saving international call termination fees.

We have now taken this to the next level by adding an “inter-office” trunk feature. Instead of using the dial plan of an extension, the trunk uses a dial plan directly. It also provides more flexibility in presenting the caller-ID: the presented caller-ID does not have to be linked to an extension. Of course this depends on the carrier’s ability and willingness to present caller-ID that aren't within the PBX address range.

Because extensions aren't charged any more, the interoffice trunk feature doesn't support prepaid accounts. Our feeling, however, is the practical relevance for this is relatively low anyway.

The term “office” goes beyond the example which I have made previously. Technically the PBX identified inbound traffic attached to a trunk, no matter if the call came from the same organization or from another source. This way, the PBX is able to perform general call routing functions and act as a general-purpose session border controller. Especially since the PBX is able to operate on multiple network interfaces, it can be used to translate traffic between LAN and WAN. Other scenarios, like translating calls between IPv4 and IPv6, or just transcoding codecs, are now also possible. Time will tell what customers want to see.

The inter-office trunk feature will be available from version 5.0.10i onwards.

Latest Articles

View All

The Vodia PBX and SAML Integration

Vodia PBX now supports SAML integration, offering a secure and standards-based method for enterprise users to access their phone system through single sign-on. SAML, or Security Assertion Markup Language, allows employees to authenticate in one system and access other systems without managing multiple passwords, improving both security and user experience. By exchanging digitally signed SAML Assertions between Identity Providers and Service Providers, Vodia ensures seamless authentication across internal and external applications. With this integration, IT teams can simplify user management, reduce login complexity, and maintain strong security controls for business communications.

September 2, 2025

Rethinking Communication in Education: Vodia Smart School

Digital communication is now woven into daily school life, from classroom platforms to how parents and teachers connect. Vodia Smart School takes this further with a VoIP-powered system that provides fast, secure, and documented communication for consent forms, sick notes, and routine notifications. In urgent situations, it enables automated alerts to staff, parents, and first responders, ensuring rapid responses when time is critical. Fully GDPR-compliant and offering features such as caller ID masking, MS Teams integration, and control of bells, announcements, and school systems, Smart School gives schools a modern, reliable alternative to legacy systems while improving both safety and everyday operations.

August 28, 2025

Vodia Now Integrates with Microsoft Teams Presence

Vodia PBX now supports Microsoft Teams Presence, building on its Teams Direct Routing certification and Dynamics 365 integration. Using Graph API from version 69.5.13, a user’s Vodia extension is automatically set to Do Not Disturb when they are on a Teams call. Presence status such as Available, Away, Busy, In a Meeting, or Presenting is matched via the Teams user’s principal username or email, allowing VoIP phones and web portals to show real-time status across devices. This integration connects Teams with a full-featured SIP-compliant PBX, enabling organizations to unify communications, streamline workflows, and support both cloud and on-premise telephony solutions.

August 25, 2025