A Complete Guide to Direct Routing
*Updated 22 September 2026*
Enterprise communications are rarely built around one platform.
An organisation may use Microsoft Teams for collaboration, Mitel for telephony, Five9 for its contact centre and Zoom elsewhere in the business. It may also need to retain existing numbers, connect multiple sites and keep critical services available during disruption.
Direct Routing helps connect those environments without automatically forcing everything onto one communications platform.
At its simplest, Direct Routing allows voice services to connect with cloud communications platforms through SIP-based infrastructure. In more complex estates, it can also provide a flexible routing layer between collaboration platforms, PBXs, contact centres and public telephone services.
This matters because hybrid communications are becoming the norm rather than the exception. Research from Techaisle and Mitel covering more than 1,900 mid-market and enterprise organisations found that 92% of organisations modernising their communications were prioritising hybrid deployment models combining cloud and existing infrastructure.
For Britannic, this is where NetX Direct Routing fits. NetX can connect platforms such as Microsoft Teams and Zoom with wider voice environments, while the underlying NetX SIP platform can integrate existing Mitel, Avaya, Cisco and contact centre technology.
The question is therefore not simply whether a business should move its telephone system to the cloud.
It is how voice should connect across the whole communications estate.
What Is Direct Routing And How Does It Work?
Direct Routing connects a communications platform with external telephone services through SIP-based voice infrastructure.
SIP, or Session Initiation Protocol, manages voice sessions across IP networks. A Session Border Controller can then provide interoperability, control and security between the communications platform and external voice services.
Microsoft uses Direct Routing specifically for connecting Teams Phone to external telephony through a supported SBC. Microsoft identifies existing carriers, third-party PBXs, analogue devices, advanced routing and complex deployments as common reasons to choose it.
Other platforms may use different terminology, including SIP connectivity or Bring Your Own Carrier, but the underlying principle is similar.
The application employees use does not necessarily have to control the complete telephone network underneath it.
Britannic's NetX Direct Routing platform provides the routing layer, while NetX SIP provides number management, routing, reporting, resilience and integration across wider enterprise voice environments.
This distinction is important.
SIP provides the voice connectivity. Direct Routing determines how that connectivity reaches communications applications and other voice systems.
For a deeper explanation of SIP itself, Britannic's SIP The Benefits, Realities and Implementation article is a useful supporting read.
When Does Direct Routing Add Real Value?
Direct Routing becomes most useful when an organisation has more complexity than one platform, one carrier and one straightforward calling requirement.
The strongest use cases usually involve integration, migration, resilience or control.
| Business Requirement | Where Direct Routing Can Help |
| Existing PBX investment |
|
| Multiple communications platforms | Connect UC, PBX and contact centre environments |
| Phased migration | Move users, sites or workloads at different times |
| Existing telephone numbers | Retain and manage established customer-facing numbers |
| Specialist contact centre | Keep dedicated CX technology separate from employee collaboration |
| Complex routing | Direct calls according to location, service or continuity requirements |
| Business continuity | Provide alternative destinations when normal routes are unavailable |
| Greater visibility | Add network-level reporting, analytics and routing control |
This is particularly relevant in organisations that do not want to redesign the entire estate simply because one part of the business adopts a new cloud platform.
Britannic's current Unified Communications proposition reflects this approach, supporting cloud, private cloud, on-premise and hybrid environments rather than treating one deployment model as universally correct.
How Does Direct Routing Fit Into A Hybrid Communications Estate?
A good Direct Routing strategy allows different technologies to perform the jobs they are best suited to.
For example, Microsoft Teams may support employee collaboration while an existing Mitel environment continues to provide core telephony. Five9 may remain the specialist contact centre, while Zoom supports another part of the organisation.
The objective is not to decide which platform should replace everything else.
It is to determine what should be retained, what needs integrating and what genuinely needs migrating.
Britannic's Mitel partnership is particularly relevant here. Mitel environments can remain part of a modern communications architecture rather than being treated as technology that must automatically be replaced.
NetX has already been used to integrate Microsoft Teams with an existing Mitel PBX, demonstrating how organisations can introduce new collaboration capability without abandoning valuable infrastructure.
The same principle applies to contact centres.
An organisation may use Teams or Zoom for employee communications while retaining Five9 Intelligent CX for customer interactions. Five9 combines voice and digital engagement with AI, automation and analytics, making it a different workload from general employee telephony.
Direct Routing and SIP can help connect those environments rather than forcing them into the same application.
What Should A Strong Direct Routing Architecture Deliver?
A good Direct Routing environment should provide more than external calling.
It should give the organisation greater control, visibility and continuity across enterprise voice.
Britannic's NetX platform provides capabilities including number management, configurable routing, visual call flows, dashboards, scheduled reporting, role-based access, fraud controls and business continuity routing. NetX is backed by a 99.999% SLA and supports integrations across platforms including Microsoft Teams, Zoom, Mitel, Avaya, Cisco and Google.
That network-level visibility becomes increasingly useful when the business operates several communications platforms.
Instead of relying exclusively on the reporting available inside each application, the organisation can see how calls are moving through the wider voice environment.
Resilience is particularly important.
A cloud communications platform may be highly available, but a telephone service can still depend on internet connectivity, carriers, SIP infrastructure, local networks and other applications.
The better continuity question is therefore:
What happens to an important inbound call if its normal destination becomes unavailable?
With suitable routing in place, calls can be directed to another site, number or platform rather than simply failing.
Britannic's updated PSTN switch-off guide expands on this wider continuity issue. Openreach confirmed in July 2026 that the legacy PSTN will retire on 31 January 2027, with approximately 350,000 business premises still connected at that point.
Security should also be designed into the routing layer.
Organisations need to consider encryption, administrative permissions, call restrictions, unusual traffic and toll fraud. NetX includes configurable monitoring, alerting and fraud controls, while Britannic's Toll Fraud guide provides more detailed advice on protecting enterprise voice environments.
How Should Businesses Plan A Direct Routing Migration?
A successful migration should begin with the existing estate rather than the destination technology.
Organisations should first establish which numbers, platforms, carriers, sites and business-critical call flows already exist.
The next decision is what each part of that estate actually needs.
Some technology should be retained because it continues to deliver value.
Some systems need integrating.
Some workloads are ready to migrate.
Others may no longer be necessary at all.
Britannic recommends considering five areas during planning:
Map the existing estate, including numbers, carriers, PBXs, contact centres and critical services.
Decide what should be retained, integrated, migrated or retired.
Connect platforms through the appropriate SIP and routing architecture.
Protect the environment through security, failover and continuity planning.
Optimise routing, reporting and performance after deployment.
This is deliberately a business-led sequence.
It prevents Direct Routing from becoming another technology project that recreates existing complexity in a different place.
St Oswald's Hospice provides a practical example. When its 20-year-old telephony environment reached the end of its contract, Britannic integrated calling into Microsoft Teams through Direct Routing and NetX SIP. The project centralised telephony across multiple sites and also identified opportunities to reduce unnecessary Microsoft licensing.
The lesson is broader than Teams.
A good migration should improve the whole operating model around voice, not simply move calls into another interface.
When Is Direct Routing Not The Right Choice?
Direct Routing is not automatically the best architecture for every organisation.
A business using one cloud communications platform with straightforward calling requirements may be better served by the platform provider's standard calling service.
Microsoft, for example, supports several PSTN connectivity models including Calling Plans, Operator Connect, Teams Phone Mobile and Direct Routing. Those models can also coexist within the same tenant.
Operator Connect can be attractive where an organisation wants a Microsoft-certified operator to manage the PSTN infrastructure without the additional responsibility associated with a Direct Routing SBC.
The decision should therefore be based on genuine requirements.
Direct Routing becomes more relevant where the organisation needs:
- Existing-system integration
- Carrier flexibility
- Advanced routing
- Phased migration
- Multiple communications platforms
- Specialist contact centre connectivity
- Additional continuity options
- Greater control over enterprise voice
Where those requirements do not exist, a simpler model may be more appropriate.
That is an important distinction because the most sophisticated architecture is not always the best architecture.
Direct Routing Should Create Flexibility Rather Than Lock-In
Direct Routing is often introduced as a way to enable external calling from a cloud communications platform.
Its strategic value is broader.
It can separate enterprise voice from the assumption that every communication workload must sit on one application.
Teams can provide collaboration.
Mitel can remain where it continues to deliver value.
Five9 can support specialist customer experience.
Zoom can provide another cloud communications option. Britannic's Zoom Phone proposition can also use NetX to retain existing carrier agreements while adopting cloud telephony.
The network underneath them can provide the common routing, visibility and continuity layer.
That gives organisations greater freedom to modernise at the pace that suits their business rather than the lifecycle of a single communications vendor.
Britannic Technologies combines NetX Direct Routing, NetX SIP, Unified Communications, Mitel, Five9, Zoom and managed services to help organisations design voice environments around business outcomes rather than individual platforms.
Organisations reviewing their voice architecture can speak to Britannic about mapping their current communications estate and identifying what should be retained, integrated, migrated or retired before selecting the most appropriate routing model.
