- •Teams supports multiple SBCs in a single tenant - dual-vendor Direct Routing is a supported configuration, not a workaround.
- •Legitimate use cases include redundancy, geographic routing, cost arbitrage, and live migration between carriers.
- •Without coordination, dual-vendor environments produce routing conflicts, number assignment collisions, STIR/SHAKEN attestation gaps, and E911 routing failures.
- •Teams Plus operates as a carrier-grade primary or secondary SBC layer, with unified analytics that eliminate the diagnostic ambiguity of multi-vendor configurations.
Yes, you can. And in a growing number of enterprise deployments, it is the right architecture.
Microsoft Teams supports multiple Session Border Controllers in a single tenant. That is not a workaround. It is a supported configuration with legitimate use cases ranging from geographic redundancy to cost arbitrage to managing a live migration. The question is not whether it is possible. The question is whether you are doing it without creating routing conflicts, attestation gaps, or number assignment collisions.
How Multiple SBCs Work in One Tenant
Teams Admin Center allows administrators to register multiple SBCs under the same tenant, each with its own FQDN, port, and capacity definition. Voice routing policies, assigned at the user level, determine the priority order of SBCs for a given call. If the first SBC in the route fails to respond within the timeout window, Teams fails over to the next one in the policy.
The net result: two vendors can coexist in a single Teams environment, handling different call populations, geographies, or user groups - without a port, a cutover, or a service interruption.
Legitimate Reasons to Run Two Vendors
Redundancy. If your primary SBC vendor has an outage, failover to a secondary keeps calls moving. Active-passive configurations are common in regulated industries where voice continuity is non-negotiable.
Geographic routing. Multinational organizations often need SBCs in different regions for PSTN break-out compliance, latency, and local emergency services. A US carrier for North American traffic and a European carrier for EMEA under the same tenant is a straightforward configuration.
Cost arbitrage. Different carriers price different call types differently. Routing specific destination prefixes through a second carrier can produce meaningful per-minute savings while domestic traffic stays on the primary. Teams routing policies support prefix-level granularity.
Migration in progress. This is the most common dual-vendor scenario. Bring the new carrier online, port a subset of numbers, validate performance, then migrate in tranches. Both carriers run in parallel until the legacy SBC is decommissioned. At no point does a wholesale port create a service gap.
What Breaks Without Coordination
Routing conflicts. If two SBCs can handle the same call type and neither is clearly prioritized, calls route to the wrong SBC and fail. Every routing policy in a dual-vendor environment needs an explicit priority sequence and a defined scope.
Number assignment collisions. Teams requires each number to be assigned to exactly one user, auto attendant, call queue, or resource account. Overlapping number ranges across two carriers, common in poorly managed migrations, produce assignment conflicts that require manual cleanup.
STIR/SHAKEN attestation gaps. If your primary carrier delivers A-level attestation and your secondary delivers B, calls through the secondary present a degraded identity signal to receiving networks. That affects answer rates, particularly on T-Mobile and AT&T. Evaluate both carriers' attestation capability before deployment, not after.
Emergency services routing. E911 must be explicitly configured for each SBC. Dynamic emergency calling, which uses Teams client location data to route 911 to the correct PSAP, must be mapped for both carriers. An unconfigured secondary can route emergency calls incorrectly or not at all.
How Teams Plus Fits
Teams Plus runs carrier-grade infrastructure designed to sit alongside an existing voice environment or replace a second vendor entirely. For enterprises in a migration, we come online as the new primary while your legacy vendor finishes out a contract. No disruptive port, no service gap. Our SBCs register in your tenant as a co-equal voice route, and traffic shifts on a schedule you control.
For enterprises running a secondary vendor for redundancy, we provide geo-redundant infrastructure across four data centers with a 99.999% uptime SLO - roughly five minutes of downtime per year. If your current secondary cannot meet that standard, your redundancy architecture is not delivering what you think it is.
We also provide unified visibility across the routing layer. When two carriers are in play and something breaks, the diagnostic question is always: which one is responsible? Our carrier-layer analytics answer that directly instead of leaving you to reconcile call records from two vendors.
