Automatic call forwardings most often fail after a migration because number configurations, IVR logic, and routing rules are not transferred one-to-one to the new environment. The solution lies in thorough preparation: document all existing forwardings before the migration, test them systematically in an acceptance environment, and ensure a failover scenario is in place on the day of go-live. In this article, we answer the most frequently asked questions about call routing after a migration, from risk assessment to recovery and the role of an external partner.
Why do automatic call forwardings fail after a migration?
Automatic call forwardings fail after a migration because the configuration in the old system is rarely fully documented and is not automatically transferred to the new platform. Routing rules, schedules, queues, and IVR menus have often grown over years and contain dependencies that only become visible when they stop working.
In a telephony or contact center migration, there are three common causes:
- Incorrect number translation: Internal extensions or DDI numbers are numbered differently in the new system, causing existing forwardings to point to a non-existent destination.
- Loss of time-based logic: Opening hours, holiday schedules, and deviating patterns are often hardcoded in the old system and are not automatically exported.
- Broken integrations: Forwardings that depend on a link with a CRM, workforce management, or external database stop working if that link is temporarily or permanently lost during the migration.
A migration is not a simple copy-paste operation. Each platform has its own way of storing routing, and what is a single setting in system A may consist of three separate configuration screens in system B.
Which call forwardings are most at risk during a migration?
The call forwardings most at risk during a contact center migration are complex, multi-layered routings that depend on external data sources, time conditions, or multiple intermediate steps. Simple fixed forwardings from number A to number B usually survive a migration without issues.
Special attention should be given to:
- IVR menus with conditional logic that choose a different route based on customer choice, time, or wait time
- Emergency scenarios and deviating routing for outages, peak traffic, or holidays that are rarely tested but critical
- Forwarding to external numbers of remote workers, external service providers, or branches with their own telephony systems
- Queue overflows that automatically forward to another team or voicemail if wait times are too long
- Skill-based routing where calls are sent to specific employees based on customer profile or language preference
These forwardings are the most vulnerable because they contain not just a destination number, but also logic, conditions, and external dependencies. In an IVR migration, it is precisely this layer that must be manually rebuilt and validated.
How do you test call forwardings before a migration go-live?
You test forwardings before go-live by creating a full test plan based on a routing matrix, running through all scenarios in an acceptance environment, and comparing the results with the behavior in the old system. Testing after the migration is too late; testing must be a formal phase within the migration project itself.
An effective testing process includes at least these steps:
- Inventory all active forwardings in the existing system, including temporary and seasonal variants.
- Build a test matrix with every unique scenario: normal office hours, after hours, holidays, peak loads, and outage situations.
- Test in an isolated acceptance environment that mimics the production environment as accurately as possible, including active integrations.
- Perform end-to-end call tests from external numbers to simulate the full path from incoming call to agent.
- Document discrepancies and resolve them before go-live, not after.
Involve the employees who work with the forwardings daily in the testing process. They know the exceptions and edge cases that are not in any technical document. Call routing after a migration is only reliable once that implicit knowledge has also been validated.
What should be included in a routing matrix to prevent migration problems?
A routing matrix is a structured overview of all forwardings, conditions, and destinations in your telephony environment. To prevent migration problems, the matrix must include at least the source number, the condition, the destination, the failover destination, and the responsible owner for each forwarding.
A complete routing matrix contains per row:
- Source number or queue: the number or channel where the call arrives
- Time condition: when does this routing apply (day, time, holiday, exception)?
- Primary destination: where does the call go under normal circumstances?
- Overflow or failover destination: what happens if the primary destination is unavailable?
- Dependencies: which systems or integrations are required for this routing?
- Test result: has this routing been tested and approved in the acceptance environment?
- Owner: who is responsible for the management and validation of this line?
A routing matrix is not a one-time document. Ensure it remains up-to-date after the migration, as organizations that neglect this will face another blind spot during the next change or migration.
How do you restore a call forwarding that no longer works after migration?
If a call forwarding stops working after migration, you restore it by first isolating the cause: is it due to an incorrect destination configuration, a broken integration, or a missing time rule? Only then do you adjust the configuration, test the fix, and document the change in the routing matrix.
Follow this step-by-step plan for a non-working forwarding:
- Reproduce the problem with a test call from an external number to confirm exactly what is going wrong and where the call drops or is misrouted.
- Compare the current configuration with the routing matrix or documentation from the old system to see what differs.
- Check dependencies: is the link with the CRM or the queue active? Are the time rules correctly set?
- Adjust the configuration in the management environment of the new system and test immediately after the change with a live test call.
- Document the cause and the solution so you can act faster if similar problems occur.
For complex IVR migrations, it is wise to maintain a higher monitoring frequency in the first weeks after go-live and have an escalation path ready for reports from employees or customers reaching the wrong destination.
When should you engage an external partner for a telephony migration?
You engage an external partner for a telephony migration when internal knowledge of routing configuration, integrations, or the new platform is insufficient to perform the migration without risk. The more complex the existing environment, the sooner external expertise pays off.
Concrete signals that external support is wise:
- The existing routing is poorly documented or not documented at all, and the knowledge resides with only one or two employees
- The new platform differs fundamentally from the old system in architecture or configuration logic
- Multiple locations, systems, or vendors are involved in customer contact
- The organization cannot afford downtime or errors in accessibility due to business-critical customer contact
- Internal IT has insufficient capacity alongside daily management tasks
An external partner adds value in three phases: before the migration by documenting and structuring the existing environment, during the migration with configuration and testing, and after with monitoring and optimization. Choose a partner that not only advises but also takes on the execution and management, so you have a single point of contact for the entire process.
How Pegamento helps with a secure migration of your contact center environment
We guide organizations through the entire migration process of their contact center environment, from the initial inventory to ongoing optimization after go-live. This means you get everything under one roof with us, without complex vendor management or separate advice that you have to implement yourself.
What we specifically do for you:
- Full routing documentation of your existing environment, including IVR logic, schedules, and integrations
- Creation of a routing matrix that serves as the foundation for the migration and subsequent management
- Configuration and testing of all forwardings in an acceptance environment before go-live
- Guidance on migration day with an active failover scenario and immediate recovery capacity
- Monitoring and optimization in the weeks after go-live to quickly identify and resolve discrepancies
We work with proven modules and smart combinations of standard building blocks that align with your processes and systems, not costly custom work. Our solutions for contact center technology and omnichannel business telephony are designed to make even complex environments manageable and future-proof. Want to know how we can guide your migration? Contact us and we will look at the best approach for your situation together.
Frequently Asked Questions
How long does it take on average to correctly document all call forwardings before a migration?
The time required for full routing documentation depends heavily on the complexity of your environment. For a medium-sized organization with multiple queues, IVR menus, and schedules, you should count on one to three weeks of intensive work. Always plan this well before the migration, so there is still time to gather missing information from employees who hold the implicit knowledge in their heads.
What is a realistic failover scenario if call forwardings fail on migration day?
A good failover scenario consists at least of a temporary redirection of critical numbers to a stable destination, such as a mobile number or an external call center, and a clear escalation path for employees to report outages immediately. Ensure this scenario is pre-configured and tested, not devised only when something goes wrong. Migration day is not the time to improvise.
Can we perform the migration in phases to limit the risk of downtime?
Yes, a phased migration is in many cases the safest approach, where you start with less critical numbers or locations and only switch to more complex routings after the first phase is stable. This gives you the chance to discover and resolve problems in a controlled environment before the entire organization runs on the new system. Discuss this approach with your provider beforehand, as not every platform supports a long-term hybrid scenario.
How do you prevent the routing matrix from becoming outdated after the migration?
Assign one owner responsible for keeping the routing matrix up to date and make updating it a standard part of the change process: no adjustment to a forwarding without the matrix being updated immediately. Ideally, link this to a change management procedure so that every change is documented, approved, and tested. Organizations that set this up structurally avoid the blind spots that immediately surface during a subsequent migration or audit.
What are the most common mistakes in an IVR migration that cost a lot of recovery work afterward?
The three most costly mistakes are: not testing emergency scenarios and holiday schedules because they are not active at the time of migration, underestimating dependencies with external systems such as CRM or workforce management, and the lack of a structured acceptance phase where end users validate the routing. It is precisely the exception situations that rarely occur that are the hardest to restore afterward because the cause is difficult to reproduce.
How do you know if an external partner has enough experience with your specific telephony platform?
Ask the partner for demonstrable experience with migrations on your specific platform, preferably with references from similar organizations in terms of size and complexity. Have them also explain how they handle the differences in configuration logic between the old and new systems, as that is exactly where most migration problems arise. A partner who only advises but leaves the execution to your internal team offers less security than a partner who takes on the entire process, including testing and monitoring.
How long should you maintain increased monitoring after a migration go-live?
Maintain increased monitoring for at least four to six weeks after go-live, as many problems with call forwardings only come to light under specific time conditions such as the first holiday, a peak moment, or an exceptionally high call volume. During this period, set low thresholds for alerts on failed routings and ensure someone is immediately available to intervene. After this stabilization period, you can switch back to regular management, preferably with a documented escalation path for future incidents.
