Troubleshoot UniFi client roaming

Goal and prerequisites

Investigate a phone or laptop that remains connected to an AP after moving closer to another one. Begin with the user's experience: a device remaining on an AP is a problem when the connection becomes unsuitable for its task, not simply because another AP is physically nearer.

Use two adopted APs, the same SSID and security configuration on both, a single client network, a phone or laptop and a marked walking route. Save the current radio and SSID settings. Apple documents that the client decides when to roam, using signal and other factors; roaming assistance helps that decision but does not create coverage where none exists. [1]

Measure before adjusting

  1. Identify the affected device. Record its model, operating system, wireless driver where applicable and SSID. Compare it with another client following the same route. A problem limited to one model deserves a client-focused investigation before changing the whole site's configuration.
  2. Check the SSID on both APs. Confirm that both advertise the intended network with matching security. Check for client-specific AP locks and remove an unintended lock. Ensure the second AP is online and that its uplink carries the client's VLAN.
  3. Make a baseline walk. Start beside AP A, confirm association and walk towards AP B while running the actual application. For a call, have the other participant note any silence or reconnection. Record the time, connected AP, signal and point where the association changes. Walk back in the other direction.
  4. Use connection telemetry. Where supported, WiFiman Mobile's Signal view can show AP transitions and connection metrics. Check the Network client history alongside it. Do not treat switching between 2.4 and 5 GHz on one AP as the same event as moving to a different AP. [2]
  5. Check coverage at the transition. Pause at the point where the first AP becomes weak. Determine whether the second AP offers a usable connection there. If both are weak, adjust placement or add coverage using Access point placement guide. Increasing a disconnect threshold would otherwise create a gap.
  6. Review the transmit-power balance. An AP that remains very strong across another AP's intended area may delay roaming. Trial a modest, recorded adjustment to the relevant radio, then repeat the whole route. Include stationary clients near the edge of that AP's coverage in the retest.

Evaluate roaming assistance

  1. Review BSS Transition. In the SSID's advanced settings, inspect BSS Transition. It can provide guidance about better candidates to compatible clients. Leave it enabled where it works correctly; test affected older clients if compatibility problems appear. [3]
  2. Test Fast Roaming separately. The Fast Roaming setting uses 802.11r to reduce authentication work during a supported handoff. Enable or retain it for compatible clients, then repeat the same walk and application. It does not guarantee a roam at a specific signal level. If only one legacy device fails after this change, test a suitable compatibility configuration for that device and document the result. [1] [3]
  3. Treat Minimum RSSI as an advanced step. UniFi can disconnect a client once its AP-observed signal falls below a configured threshold. The client then chooses where to reconnect and may choose the same AP. An aggressive setting can therefore cause repeated drops. Use it only after a survey confirms an alternative usable AP throughout the intended handoff area. [4]
  4. If needed, trial a measured threshold on one radio. Record edge-of-cell readings from several affected clients. Select a cautious threshold based on those observations, change only one AP/radio and test both mobile and fixed devices. Do not copy one numeric threshold to every AP and band. Revert if the result is unstable.

Verify the improvement

Use a small results sheet with columns for client, walking direction, starting AP, transition location, application interruption and final AP. Run the route at least three times before and after the selected change. Check whether a roam actually occurred and whether the application improved.

Also test a stationary device at the weak edge, such as a printer or smart-home accessory. A change that helps a phone during a walk can disconnect an immobile device that has no better AP available. Assess the whole intended client population.

Troubleshooting and recovery

If the client loses its IP address while changing APs, investigate VLAN consistency and DHCP rather than assuming a radio-handoff problem. If the second AP never becomes a candidate, verify that it broadcasts the same SSID and supports the client's selected band and security.

Undo new Minimum RSSI or roaming changes in reverse order until the baseline behaviour returns. Keep the setting that demonstrably improves the required application, and document any separate compatibility SSID. A temporary Wi-Fi toggle can help diagnose which AP the client chooses from a fresh connection, but it is not a substitute for solving recurring roaming problems.

Sources

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