Wireless Engineer Interview Questions

By adminFairness In Tech, Kindness In Tech
20 Non-Vendor Specific Wireless Engineer Interview Questions
  1. Explain the difference between 2.4 GHz and 5 GHz bands in terms of coverage and interference.
  2. What are the key differences between WPA2 and WPA3?
  3. What is DFS, and why is it important in wireless networks?
  4. How does MIMO improve wireless performance?
  5. Describe the purpose of a site survey. What types are there?
  6. What is RSSI, and how does it differ from SNR?
  7. Explain channel bonding and its impact on Wi-Fi performance.
  8. What is roaming in Wi-Fi, and what mechanisms facilitate seamless roaming?
  9. Define airtime fairness and why it matters in WLAN design.
  10. Explain band steering and how it benefits the network.
  11. What is hidden node problem, and how can it be mitigated?
  12. Describe the purpose of beacon frames in Wi-Fi.
  13. What are management, control, and data frames in 802.11? Provide examples.
  14. Explain the concept of co-channel and adjacent channel interference.
  15. How would you troubleshoot poor wireless performance reported by users?
  16. Describe how you would design wireless coverage for a high-density area such as a stadium or auditorium.
  17. What is OFDMA and how does it improve Wi-Fi efficiency?
  18. Explain the difference between PSK and Enterprise authentication modes.
  19. What is Fast BSS Transition (802.11r), and when would you enable it?
  20. How would you secure guest wireless access in an enterprise environment?

2. 10 Aruba Specific Wireless Interview Questions

  1. What is Aruba AirMatch, and how does it differ from ARM (Adaptive Radio Management)?
  2. Explain the role of Mobility Master in Aruba architecture.
  3. How does Aruba ClearPass integrate with Aruba WLAN for network access control?
  4. What is UCC in Aruba WLAN, and how is it configured?
  5. Describe the purpose of Virtual Controller in Instant AP deployments.
  6. How do you configure RF optimization in an Aruba deployment?
  7. What is AppRF, and how does it benefit Aruba WLAN deployments?
  8. Explain how Aruba’s ClientMatch works.
  9. Describe the difference between a standalone controller and Mobility Conductor in Aruba OS 8.
  10. How does Aruba implement Dynamic Segmentation, and what problem does it solve?

3. 10 Cisco Specific Wireless Interview Questions

  1. Explain the difference between AireOS and IOS-XE based controllers (e.g., 5508 vs. 9800).
  2. What is Cisco FlexConnect, and when would you use it?
  3. Describe how Cisco CleanAir works and its benefits.
  4. What is the purpose of Mobility Groups in Cisco WLAN deployments?
  5. Explain how Cisco AP performs RRM (Radio Resource Management).
  6. Describe the process of setting up Central Web Authentication in Cisco wireless.
  7. How does Cisco implement Fast Secure Roaming (802.11r, CCKM)?
  8. What is the role of Mobility Anchors in Cisco WLAN solutions?
  9. How do you troubleshoot AP join issues on a Cisco WLC?
  10. Explain the concept of SSO (Stateful Switchover) in Cisco wireless controllers.

Wireless Engineer Interview Questions – Acceptable Answers

  1. 2.4 GHz vs 5 GHz:
    • 2.4 GHz: better range, more interference (microwaves, Bluetooth).
    • 5 GHz: less interference, more channels, shorter range due to higher frequency absorption.
  2. WPA2 vs WPA3:
    • WPA3 uses SAE for authentication (resistant to offline dictionary attacks), stronger encryption (192-bit suite in enterprise), and forward secrecy.
  3. DFS (Dynamic Frequency Selection):
    • Allows use of radar channels (UNII-2, UNII-2e), requires detection and vacating if radar detected.
  4. MIMO:
    • Multiple Input Multiple Output; uses multiple antennas to transmit/receive simultaneously, increasing throughput and reliability.
  5. Site Survey Types:
    • Predictive (simulation), Passive (listening to RF environment), Active (client associated tests), APoS (AP on a Stick).
  6. RSSI vs SNR:
    • RSSI: received signal strength.
    • SNR: signal-to-noise ratio; difference between signal and noise, key indicator of link quality.
  7. Channel Bonding:
    • Combining two adjacent channels (e.g. 40 MHz or 80 MHz) to increase throughput; can cause interference in congested environments.
  8. Roaming:
    • Client moving between APs; facilitated by 802.11r, OKC, or vendor proprietary fast roaming protocols.
  9. Airtime Fairness:
    • Allocates equal transmission time rather than equal data, preventing slow clients from degrading network performance.
  10. Band Steering:
    • Encourages dual-band clients to connect to 5 GHz rather than 2.4 GHz for better performance.
  11. Hidden Node Problem:
    • Two clients out of range of each other but both in range of AP, causing collisions. Mitigated by RTS/CTS.
  12. Beacon Frames:
    • Sent by APs to advertise SSID, capabilities, supported rates, and maintain synchronization.
  13. 802.11 Frame Types:
    • Management (Beacon, Probe, Authentication), Control (RTS, CTS, ACK), Data (actual user traffic).
  14. Co-channel vs Adjacent Channel Interference:
    • Co-channel: same channel, sharing bandwidth but can coordinate.
    • Adjacent channel: overlapping channels, causes more interference.
  15. Troubleshooting Poor Performance:
    • Check SNR, client drivers, AP placement, channel utilization, interference, coverage gaps, capacity limits.
  16. High-Density Design:
    • Lower TX power, more APs with directional antennas, smaller cell sizes, careful channel planning, possibly using 5 GHz only.
  17. OFDMA:
    • Orthogonal Frequency Division Multiple Access; divides channel into sub-carriers for simultaneous transmission to multiple clients, improving efficiency (Wi-Fi 6/6E).
  18. PSK vs Enterprise:
    • PSK: shared key, simple.
    • Enterprise: 802.1X authentication with RADIUS, per-user credentials, more secure.
  19. Fast BSS Transition (802.11r):
    • Allows quick handoff between APs without re-authentication delay, useful for VoIP or roaming critical apps.
  20. Securing Guest Access:
    • Separate VLAN, captive portal, bandwidth limiting, firewall rules to isolate from internal network.

Aruba Specific Wireless Interview Questions – Possible Answers

  1. AirMatch vs ARM:
    • AirMatch (OS8) is AI-driven and considers historical trends; ARM (OS6) is reactive for channel/power optimization.
  2. Mobility Master:
    • Centralized controller for configuration, policy, and firmware management across multiple Mobility Controllers.
  3. ClearPass Integration:
    • Acts as RADIUS server for 802.1X authentication, guest access, device profiling, posture assessment.
  4. UCC (Unified Communications & Collaboration):
    • Prioritizes real-time traffic (VoIP, video) using enhanced QoS policies.
  5. Virtual Controller:
    • In IAP clusters, one AP acts as controller managing others, eliminating need for dedicated controller hardware.
  6. RF Optimization:
    • Uses ARM/AirMatch to adjust channels, power levels, band steering, and ClientMatch for optimal performance.
  7. AppRF:
    • Application visibility and control feature to classify and prioritize application traffic.
  8. ClientMatch:
    • Steers clients to best AP based on performance and load, addressing sticky client issues.
  9. Standalone Controller vs Mobility Conductor:
    • Standalone: controller manages its own config. Mobility Conductor centralizes configuration and manages controllers under it.
  10. Dynamic Segmentation:
    • Uses ClearPass + user role to apply VLANs dynamically, ensuring consistent policy regardless of connection method.

3. Cisco Specific Wireless Interview Questions – Possible Answers

  1. AireOS vs IOS-XE Controllers:
    • AireOS (5508, 5520) is legacy with monolithic architecture. IOS-XE (9800) is modern, modular, integrates with SD-Access.
  2. FlexConnect:
    • Allows APs to switch traffic locally at remote sites while still managed centrally by WLC, useful for WAN outages.
  3. CleanAir:
    • Uses specialized chipset to detect, identify, and locate non-Wi-Fi interference sources (e.g. microwaves, Bluetooth).
  4. Mobility Groups:
    • Allow seamless roaming between controllers by sharing client information, enabling Layer 3 roaming.
  5. RRM:
    • Radio Resource Management dynamically adjusts channels and power based on environment, client load, and interference.
  6. Central Web Authentication:
    • Redirects unauthenticated clients to external/internal web portal for login via ISE or other NAC solution.
  7. Fast Secure Roaming:
    • 802.11r for FT, CCKM (Cisco Centralized Key Management) for fast reauthentication without full EAP exchange.
  8. Mobility Anchors:
    • Controllers configured to terminate guest or tunneled traffic, often for DMZ guest internet breakout.
  9. AP Join Troubleshooting:
    • Check AP reachability, DHCP Option 43 or DNS for controller discovery, correct software versions, certificates, CAPWAP UDP ports (5246/5247).
  10. SSO (Stateful Switchover):
    • High availability feature; standby WLC maintains active state, ensuring client sessions remain during failover.

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