WLC interview questions and answers

Wireless Interview Questions & Answers --

Q1. What is Wi-Fi and what is WIMAX?

• Wi-Fi: Wireless Fidelity, a technology that uses radio waves for high-speed network connectivity based on IEEE 802.11 standards. Devices include PCs, laptops, video game consoles, phones, tablets, smart TVs, and more.
• WiMAX: Worldwide Interoperability for Microwave Access, referenced by IEEE 802.16, commonly termed 4G. It provides wide area network access and uses OFDM modulation.

Q2. What is 802.1x?

• 802.1x: IEEE standard for port-based network access control, providing an authentication framework for wireless LANs. It authenticates devices wishing to attach to a LAN or WLAN through a central authority.

Q3. Which encryption type does WPA2 use?

• WPA2 uses AES: A newer Wi-Fi encryption solution that is more secure than the older TKIP used in WPA.

Q4. When 2 laptops wirelessly connected can communicate directly, what type of topology is created?

• Full Mesh Topology (Ad-hoc Network): Each node is directly connected to all other nodes.

Q5. What is Piggybacking in the context of Wi-Fi?

• Piggybacking: Unauthorized use of someone else's wireless connection without their permission.

Q6. What is the frequency range of the 802.11a standard?

• 5GHz Frequency.

Q7. What is the frequency range of the 802.11g standard?

• 2.4GHz Frequency.

Q8. What is the data rate of the 802.11a standard?

• Up to 54Mbps.

Q9. What is the data rate of the 802.11g standard?

• Up to 54Mbps.

Q10. Why is WPA encryption preferred over WEP?

• Stronger Encryption: WPA provides better security and dynamic key changes, unlike WEP which uses static keys.

Q11. What is IBSS and BSS?

• IBSS (Independent Basic Service Set): Direct device-to-device communication without a central device.

• BSS (Basic Service Set): Wireless LAN established using an Access Point.

Q12. What is ESS?

• ESS (Extended Service Set): Created by connecting multiple BSSs via a distribution system, allowing larger coverage and seamless client roaming.

Q13. What is EAP?

• EAP (Extensible Authentication Protocol): Used in wireless communications for user authentication through an Access Point and an authentication server.

Q14. What is a Wi-Fi Hotspot?

• Wi-Fi Hotspot: Physical location providing Internet access via a wireless local area network using a router connected to an ISP.

Q15. What are the different modes of a Cisco Access Point (AP) operation?

• Modes Include: Local, REAP, Monitor, Rogue Detector, Sniffer.

Q16. What is Fast Roaming?

• Fast Roaming: Device handshakes with a new AP before roaming to ensure seamless transition and avoid re-authentication.

Q17. What are the authentication mechanisms supported by Cisco Access Points?

• Mechanisms Include: WEP, WPA, WPA2, EAP, MAC authentication.

Q18. What is World Mode?

• World Mode: Adjusts channel and power settings of client devices based on geographic location.

Q19. Which devices can interfere with wireless network operation?

• Interfering Devices: Microwave ovens, cordless phones.

Q20. What is Dynamic Transmit Power Control (DTPC)?

• DTPC: Adjusts transmit power of APs and clients to ensure balanced communication and save battery life.

Q21. What are the basic parameters to configure on a wireless access point?

• Parameters Include: SSID, RF, Channel authentication method.

Q22. How do we prevent loops on the WLC?

• STP (Spanning Tree Protocol): Enabled to prevent network loops.

Q23. What is the master controller mode on WLC?

• Master Controller Mode: Designates a controller as the tie-breaker when multiple controllers are available.

Q24. What is the function of WLAN on WLC?

• WLAN: Similar to SSID, required for client association with the network.

Q25. Is there any way to recover my password for WLC?

• Password Recovery: Use the CLI and Restore-Password command for versions 5.1 and later; otherwise, reset to factory defaults.

Q26. What is FlexConnect in Cisco Wireless?

• FlexConnect: Enables branch office APs to be managed from a central location, allowing local client data switching and authentication.

FlexConnect (previously known as Hybrid Remote Edge Access Point or H-REAP) is a wireless solution for branch office and remote office deployments. It enables you to configure and control access points in a branch or remote office from the corporate office through a wide area network (WAN) link without the deployment of a controller in each office. The FlexConnect access points (APs) can switch client data traffic locally and perform client authentication locally. When they are connected to the controller, they can also send traffic back to the controller.

Q27. What is the difference between CAPWAP and LWAPP?

• CAPWAP vs LWAPP: CAPWAP supports both IPv4 and IPv6, provides better security, and uses DTLS, whereas LWAPP only supports IPv4 and is less secure.

Q28. Major differences between Cisco 2500 Series and 5500 Wireless Controllers?

• Cisco 2500 vs 5500: 5500 supports more APs and clients, offers higher throughput, and advanced features compared to 2500.

Q29. Models of Outdoor Rugged Access Points/Bridges?

• Models Include: Aironet 1530, 1540, 1560, 1570, 1552, and Industrial Wireless 3702.

Below are some of the latest Cisco Outdoor Rugged Access Points - ? Aironet 1530 Series ? Aironet 1540 Series ? Aironet 1560 Series ? Aironet 1570 Series ? Aironet 1552 Access Point ? Industrial Wireless 3702

Q30. Cisco 5520 Wireless Controller supports how many clients and APs?

• Supports Up to 1500 Access Points.

Q31. What are the main factors affecting Wireless Network?

• Factors Include: Distance, obstructions, wireless standard, signal sharing, and network interference.

Q32. Difference between Ad-Hoc and Infrastructure topology?

• Ad-Hoc vs Infrastructure: Ad-Hoc is peer-to-peer, whereas Infrastructure relies on a central Access Point.

Q33. Difference between UWB and Wi-Fi?

• UWB vs Wi-Fi: UWB is short-range and high-bandwidth, ideal for personal area networks; Wi-Fi is longer-range and suitable for local area networks.

Q34. Difference between Wi-Fi and Bluetooth?

• Wi-Fi vs Bluetooth: Wi-Fi is for high-speed internet access; Bluetooth is for short-range communication between devices.

Q35. Changes in WLAN-11ac compared to previous versions?

• 802.11ac Enhancements: Includes Multi-User MIMO, wider RF channels, and more spatial streams for faster and more efficient network performance.

There are 2 variants of 802.11ac – phase 1 and phase 2. 802.11ac is faster compared to previous standards because of the introduction of the below

• Multi-User MIMO (MU-MIMO) - Clients get on and off the network quicker, allowing more clients to be served, Pre Wave 2 an access point would talk to the clients one at a time and this was called SU-MIMO. Multi-user MIMO is important because it allows access points and their many antennas to transmit (or talk) to multiple client devices all at the same time. This helps maximize air-time efficiency so that each client, regardless of what version of 802.11 it is running, gets the amount of airtime it’s supposed to get based on the technology supported.
• Wider RF Channels - Wave 2 improvement is the option to use 160-MHz channel widths. That’s double what we saw with Wave 1 technology. Think of this as a 2 line interstate road where two additional lines have been added. The top speeds depend on the whether the AP supports 80-MHz or 160-MHz channels, as well as whether the wireless client devices tapping your network support Wave 2.
• Four Spatial Streams - Wave 2 also supports four transmitting and receiving antennas while the previous iteration supported only three receive antennas. Just like we see in the image below, With 4 spatial streams an AP could send 4 streams of data to the same client at the same time. The client can then aggregate this 4 streams and thus improve its throughput. It is also important to notice that on the AP side, the greater the number of receive antennas, the greater the distance that a particular data rate can be sustained.