hardMultiple Choice
CCNP Mesh Network Backhaul Practice Question
A network engineer is deploying a wireless mesh network using outdoor access points. The mesh APs are configured to use 802.11a/n on the 5 GHz band for backhaul and 802.11b/g/n on the 2.4 GHz band for client access. The engineer notices that the mesh backhaul links are unstable and have high packet loss. What is the most likely cause of the instability?
⚠ Common exam trap
Candidates may assume that co-channel interference is always the culprit when mesh backhaul is unstable. However, in this scenario, the backhaul is on a dedicated radio using 5 GHz, so interference is unlikely. The real trap is overlooking the range limitations of the 5 GHz band and assuming that higher frequency always performs better for backhaul.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The 2.4 GHz band provides better range for backhaul than the 5 GHz band.
The instability is most likely due to the use of the 5 GHz band for backhaul. While 5 GHz offers higher throughput, it has significantly shorter range and greater attenuation than 2.4 GHz. In an outdoor mesh network, APs may be spaced far apart, and obstacles can cause packet loss on the 5 GHz link. The 2.4 GHz band would provide better range and stability for backhaul, making option D the correct answer.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The 5 GHz band is being used for both backhaul and client access, causing co-channel interference.
Why it's wrong here
The stem explicitly states that the 5 GHz band is dedicated to backhaul and is not used for client access, so co-channel interference from simultaneous client traffic on the same radio does not occur. If both backhaul and client access shared the 5 GHz radio, co-channel interference could be a valid concern, but that is not the scenario described. The instability is better attributed to the inadequate propagation characteristics of 5 GHz at the required range.
- ✗
The 802.11a/n standard is obsolete and does not support mesh networking.
Why it's wrong here
802.11a/n is not obsolete; it remains a viable standard for many enterprise and service-provider mesh deployments, particularly for backhaul links. Mesh networking is a Layer 2 or Layer 3 capability defined by vendor protocols (e.g., LWAPP, CAPWAP) and is not prohibited by the 802.11 amendment. Therefore, the problem is not the standard but the chosen frequency band.
- ✗
The mesh APs require a wired Ethernet connection to the root AP.
Why it's wrong here
Mesh APs are specifically designed to connect to a root AP wirelessly, eliminating the need for an Ethernet drop at each AP. Only the root AP typically requires a wired uplink to the LAN; the other mesh APs relay traffic over the air. Requiring wired Ethernet would defeat the entire purpose of a mesh deployment and is not a characteristic of 802.11a/n mesh networks.
- ✓
The 2.4 GHz band provides better range for backhaul than the 5 GHz band.
Why this is correct
The 2.4 GHz band offers superior range and wall penetration compared to 5 GHz due to its longer wavelength and lower free-space path loss at equivalent transmit power. Using 5 GHz for backhaul likely results in marginal signal strength at the receiving AP, causing intermittent instability as environmental attenuation fluctuates. In contrast, 2.4 GHz would provide a more robust, stable backhaul link, even though it has fewer non-overlapping channels.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.