N10-009 Question 321
Single answerA company has deployed multiple wireless access points throughout a two-floor office to support VoIP handsets and laptops. Users report that calls drop for several seconds when they walk from one side of the building to the other, even though they quickly reconnect afterward. A site survey shows good signal strength in the affected areas, and there is no significant RF interference. The SSID and security settings are identical on all APs, but some APs are configured with much higher transmit power than others. Which of the following is the MOST likely cause of the problem?
- A
Channel overlap between adjacent 5 GHz access points is causing persistent co-channel interference
- B
Roaming is misconfigured because uneven AP transmit power is causing clients to remain associated to distant APs too long
- C
Insufficient wireless coverage is creating dead zones that force clients to disconnect and reconnect
- D
WPA3 encryption overhead is degrading signal quality during handoffs
Show answer and explanation
Correct answer: B
Explanation
The most likely issue is roaming misconfiguration caused by uneven AP transmit power. In multi-AP environments, especially those supporting voice, APs should be designed for predictable overlap and similar cell boundaries. If one AP is transmitting much more strongly than neighboring APs, clients may remain associated with it even after moving closer to another AP. This creates delayed roaming, often called sticky-client behavior, which can interrupt real-time traffic such as VoIP. Network+ objectives commonly test the ability to distinguish between insufficient coverage, interference, and roaming issues. Vendor design guides and wireless best practices consistently recommend proper RF site surveys, minimizing excessive power mismatches, and designing for controlled overlap to support seamless roaming.
- A. Incorrect.
This is incorrect. Channel planning problems can affect performance, but the scenario explicitly states there is no significant RF interference and that signal strength is good. Also, 5 GHz has more non-overlapping channels than 2.4 GHz, making overlap less likely to be the primary cause in this case. The symptom described is delayed roaming and brief call drops during movement, which more directly points to roaming behavior rather than RF contention.
- B. Correct.
This is correct. When AP transmit power levels are inconsistent, clients may continue to hold onto a weaker, farther AP instead of roaming promptly to a nearer one. This is a common sticky-client problem and a classic roaming misconfiguration issue. For latency-sensitive applications such as VoIP, delayed reassociation during movement can cause audible drops or several seconds of interruption. Best practice is to use planned cell sizing and balanced transmit power so clients roam at appropriate thresholds.
- C. Incorrect.
This is incorrect. The site survey indicates good signal strength in the affected areas, which argues against dead zones or insufficient coverage. Coverage problems typically produce complete loss of connectivity or low RSSI in specific locations, not a pattern of users staying connected too long to the wrong AP while moving.
- D. Incorrect.
This is incorrect. WPA3 does not inherently cause roaming interruptions of this type, and encryption overhead is not a recognized explanation for several-second drops during movement when coverage and interference are otherwise acceptable. A candidate might choose this if confusing security processing with roaming behavior, but the issue described is much more consistent with RF design and client roaming thresholds.