Ethernet, Switching and Wireless Interview Questions

All 94 questions

1. What is a VLAN, and why would you use VLANs to separate groups of devices?

   Asked in 6 of 337 interviews · last asked Oct 21 · Concept · Junior

   Show answer

   A VLAN, or Virtual Local Area Network, splits a physical network into separate logical networks. Each VLAN has its own broadcast domain, so broadcasts stay within that VLAN. VLANs separate groups such as staff, guests, and servers, reduce broadcast traffic, and allow access rules between groups.

   • Devices can share physical switches while belonging to different VLANs.
   • Traffic between VLANs needs routing, with firewall rules or access lists to control access.
   • Trunk links usually use IEEE 802.1Q tags to carry traffic for multiple VLANs.
   • VLANs provide separation, not encryption.

   What the interviewer checks: The interviewer checks whether you understand logical separation, broadcast boundaries, and how traffic moves between VLANs.

   Other ways it was asked

   • “What is a VLAN?”
   • “What is a VLAN, in your own words?”
   • “What are VLANs, and how do they work?”

2. Can you explain the difference between single-mode and multimode fiber?

   Asked in 3 of 337 interviews · last asked Apr 7 · Concept · Junior

   Show answer

   Single-mode fiber has a small core and carries one light mode, so it supports longer distances. Multimode fiber has a larger core and carries several light modes, which spread out and limit distance. Multimode is common for short links inside buildings, while single-mode is common for long-distance links.

   • Single-mode cores are about 9 micrometers wide; multimode cores are usually 50 or 62.5 micrometers.
   • Multimode has modal dispersion: different light paths cause pulses to spread out.
   • Multimode transceivers are often cheaper, but total cost depends on speed and distance.
   • Both support high speeds; maximum reach depends on the fiber type and transceivers.

   What the interviewer checks: The interviewer checks whether you can connect core size and light modes to distance, speed, and cost.

   Other ways it was asked

   • “What are the differences between multimode and single-mode fiber?”
   • “What is the difference between single-mode and multimode fiber?”

3. What is the difference between a VLAN and a subnet?

   Asked in 2 of 337 interviews · last asked Jun 20 · Concept · Mid-level

4. What do you know about spanning tree—what is it for, and why is it important?

   Asked in 2 of 337 interviews · last asked Apr 27 · Concept · Junior

   Other ways it was asked

   • “Tell me about spanning tree and why it is important.”

5. When an Ethernet frame arrives at a switch, what does the switch examine to decide which port to forward it through?

   Asked once · last asked Jan 29 · Concept · Junior

6. When a device sends a frame through a new switch and the destination is unknown, what does the switch do?

   Asked once · last asked Jan 29 · Scenario · Junior

7. How can devices in two different VLANs communicate with each other?

   Asked once · last asked Jan 29 · Concept · Mid-level

   Other ways it was asked

   • “If the switch is Layer 2 only, how can devices in different VLANs communicate?”

8. What is the difference between a tagged and an untagged VLAN port?

   Asked once · last asked Feb 3 · Concept · Mid-level

9. How could you connect a copper-only switch to a fiber network?

   Asked once · last asked Feb 3 · Scenario · Mid-level

10. An access point has been added to a Meraki wireless controller and shows a blue LED. What does that indicate, and how would you troubleshoot it and test connectivity from a phone?

    Asked once · last asked Feb 24 · Scenario · Mid-level

11. How do you use RF tagging and troubleshoot access points on a Cisco 9800 controller?

    Asked once · last asked Feb 24 · Tooling · Mid-level

12. What is a major difference between pairing two Nexus switches and stacking Catalyst 3850 switches, and what underlying technology accounts for that difference?

    Asked once · last asked Mar 6 · Concept · Mid-level

13. What does the vPC peer-switch command do on Cisco Nexus switches?

    Asked once · last asked Mar 6 · Concept · Mid-level

14. What command do you configure under a port channel to add it to a vPC?

    Asked once · last asked Mar 6 · Tooling · Mid-level

15. What is an orphan port in a Nexus VPC implementation?

    Asked once · last asked Mar 6 · Concept · Mid-level

16. What does it mean to have a root bridge and a secondary root, and how would you configure them?

    Asked once · last asked Mar 6 · Tooling · Mid-level

17. What mechanisms can you use to prevent spanning-tree loops?

    Asked once · last asked Mar 6 · Concept · Mid-level

18. What is storm control, and when would you use it on a network switch?

    Asked once · last asked Mar 6 · Concept · Mid-level

19. Why wouldn’t you configure an access point to transmit at maximum power everywhere?

    Asked once · last asked Mar 6 · Concept · Mid-level

20. If a port channel has two 10-gigabit links carrying a traffic session, what is the maximum bandwidth that session can use?

    Asked once · last asked Mar 6 · Scenario · Mid-level

    Other ways it was asked

    • “Why might a single traffic session on a port channel with two 10-gigabit links be limited to one link's bandwidth?”

21. What steps do you take when building and configuring network switches?

    Asked once · last asked Mar 20 · Tooling · Mid-level

22. What does it mean to collapse or simplify the layers in a switching network?

    Asked once · last asked Mar 23 · Concept · Mid-level

23. What are the various fields in the Ethernet frame format?

    Asked once · last asked Mar 28 · Concept · Junior

24. How would you design VLANs for CCTV and a corporate network in the same environment?

    Asked once · last asked Apr 6 · Design · Mid-level

25. How would you configure VLAN 1030 on a switch?

    Asked once · last asked Apr 8 · Scenario · Junior

26. How would you configure switch ports as trunk ports?

    Asked once · last asked Apr 8 · Scenario · Junior

27. Which show commands would you use to verify a switch's VLAN, trunk, VTP, and STP configuration?

    Asked once · last asked Apr 8 · Tooling · Junior

28. How would you configure a switch as a VTP client?

    Asked once · last asked Apr 8 · Scenario · Junior

29. How would you configure a switch for proper operation of the Spanning Tree Protocol (STP)?

    Asked once · last asked Apr 8 · Scenario · Junior

30. What is VTP transparent mode?

    Asked once · last asked Apr 8 · Concept · Junior

31. What is VTP pruning?

    Asked once · last asked Apr 8 · Concept · Junior

32. What is the minimum and maximum distance over which two switches in different buildings can be connected?

    Asked once · last asked Apr 15 · Concept · Mid-level

33. Which Cisco Catalyst switch models support VSS?

    Asked once · last asked Apr 15 · Concept · Mid-level

34. What is the difference between StackWise and VSS?

    Asked once · last asked Apr 15 · Concept · Mid-level

35. Where do you configure the guest splash page in the wireless controller?

    Asked once · last asked Apr 15 · Tooling · Mid-level

36. Can you explain the difference between a VLAN and a VRF?

    Asked once · last asked Apr 27 · Concept · Mid-level

37. What is the biggest difference between a virtual port channel on two Nexus switches and a port channel on two stacked Catalyst switches?

    Asked once · last asked Apr 27 · Concept · Senior

38. What DWDM interfaces are used, and how do service distances affect DWDM deployment?

    Asked once · last asked May 7 · Concept · Senior

39. If two Nexus switches are vPC peers and their peer link goes down, what happens to the vPC ports connected to the servers?

    Asked once · last asked Jun 11 · Scenario · Senior

40. In a Cisco Nexus vPC setup, how can you prevent the issue caused by a peer-link failure without manually shutting down the secondary switch, and how would you configure it?

    Asked once · last asked Jun 11 · Scenario · Senior

41. In a Nexus vPC setup, what happens if the peer link is up but the keepalive link is down?

    Asked once · last asked Jun 11 · Scenario · Senior

42. What protocols run over Ethernet?

    Asked once · last asked Jul 16 · Concept · Junior

43. How do you crimp twisted-pair Ethernet cable?

    Asked once · last asked Jul 16 · Tooling · Junior

44. Which wiring scheme do you use when crimping twisted-pair Ethernet cable?

    Asked once · last asked Jul 16 · Tooling · Junior

45. How do you use RJ45 color coding to make a straight-through Ethernet cable?

    Asked once · last asked Jul 17 · Tooling · Junior

46. How can you provide network high availability for a new server with two network interfaces?

    Asked once · last asked Jul 28 · Scenario · Mid-level

47. What are the risks and rewards of using LTE, 5G, or satellite connectivity for business sites?

    Asked once · last asked Aug 4 · Scenario · Mid-level

    Other ways it was asked

    • “What risks should businesses consider when using LTE, satellite, or other wireless WAN connectivity?”

48. What are the main considerations when integrating Bluetooth into an IoT system?

    Asked once · last asked Aug 6 · Concept · Mid-level

49. How does Bluetooth Low Energy work, and when would you use it?

    Asked once · last asked Aug 6 · Concept · Mid-level

50. What steps do you take for RF optimization?

    Asked once · last asked Aug 6 · Scenario · Mid-level

51. If you see intermittent connection drops only on Wi-Fi, what would you check next?

    Asked once · last asked Sep 1 · Scenario · Mid-level

    Other ways it was asked

    • “If you see intermittent drops only on Wi Fi, what's your next check?”

52. If wired connectivity is stable but Wi-Fi connectivity is not, which specific Wi-Fi settings would you check first?

    Asked once · last asked Sep 1 · Scenario · Mid-level

    Other ways it was asked

    • “If wired is clean but WiFi isn't, then what specific Wi Fi settings would you look at first?”

53. What are the benefits of using link aggregation between distribution switches?

    Asked once · last asked Sep 18 · Concept · Mid-level

54. How does Layer 2 spanning tree work?

    Asked once · last asked Sep 18 · Concept · Mid-level

55. How would you design Spanning Tree Protocol for a network?

    Asked once · last asked Sep 18 · Design · Senior

56. Where would you implement BPDU Guard in a network?

    Asked once · last asked Sep 18 · Scenario · Mid-level

57. What is the difference between an STP root port and a root bridge?

    Asked once · last asked Sep 18 · Concept · Mid-level

58. Which switch would you choose as the STP root bridge in a network design?

    Asked once · last asked Sep 18 · Design · Mid-level

    Other ways it was asked

    • “Why might a distribution switch be chosen as the STP root bridge?”

59. What values or symptoms would make you suspect optics or fiber issues even when the interface stays up?

    Asked once · last asked Sep 25 · Scenario · Senior

60. Why might moving from a multi-MZ to a single-MZ solution improve latency while roaming?

    Asked once · last asked Oct 19 · Concept · Senior

61. What would you do first if you noticed a drop in network coverage in an area?

    Asked once · last asked Oct 20 · Scenario · Mid-level

62. How do you configure a Cisco switch?

    Asked once · last asked Oct 21 · Tooling · Mid-level

63. How do you conduct predictive and passive wireless surveys using Ekahau?

    Asked once · last asked Oct 22 · Tooling · Mid-level

64. What is required for a client to connect to Wi‑Fi 6E on the 6 GHz band, including the security protocol and Windows version?

    Asked once · last asked Oct 22 · Concept · Mid-level

65. What type of interface is Ethernet?

    Asked once · last asked Jul 16 · Concept · Junior

66. What is a MAC address?

    Asked once · last asked Feb 3 · Concept · Junior

67. What are the standard jacket colors for multimode and single-mode fiber?

    Asked once · last asked Feb 3 · Concept · Junior

68. What are the negative effects of a spanning-tree loop?

    Asked once · last asked Mar 6 · Concept · Junior

69. With STP, do you recall the default bridge priority value?

    Asked once · last asked Mar 6 · Concept · Junior

70. For a switch to become the root bridge, is a lower or higher priority value better?

    Asked once · last asked Mar 6 · Concept · Junior

71. When you run the `show interfaces status` command on a switch, what information does it display?

    Asked once · last asked Mar 6 · Tooling · Junior

72. Can identical switch hostnames cause spanning-tree problems?

    Asked once · last asked Mar 23 · Concept · Mid-level

73. What is framing at the data link layer?

    Asked once · last asked Mar 28 · Concept · Junior

74. What is CRC?

    Asked once · last asked Mar 28 · Concept · Junior

75. Which standard defines Ethernet?

    Asked once · last asked Mar 28 · Concept · Junior

76. Can you name an IEEE standard protocol used in computer networks?

    Asked once · last asked Mar 28 · Concept · Junior

77. What is a piconet?

    Asked once · last asked Mar 28 · Concept · Junior

78. What is IEEE 802.1Q?

    Asked once · last asked Apr 8 · Concept · Junior

79. What is the Spanning Tree Protocol (STP)?

    Asked once · last asked Apr 8 · Concept · Junior

80. What is a trunk port?

    Asked once · last asked Apr 8 · Concept · Junior

81. What is a network media converter?

    Asked once · last asked Apr 15 · Concept · Junior

82. Why do we use VSS technology?

    Asked once · last asked Apr 15 · Concept · Mid-level

83. Can both links in a virtual port channel or a port channel across stacked switches be active at the same time?

    Asked once · last asked Apr 27 · Concept · Mid-level

84. Can you tell me what FlexConnect is?

    Asked once · last asked Apr 27 · Concept · Mid-level

85. What is STP, and how does it prevent network loops?

    Asked once · last asked May 26 · Concept · Junior

86. What is Ethernet, and what is it used for?

    Asked once · last asked Jul 16 · Concept · Junior

87. What layer do VLANs operate at, and what is the function of a VLAN?

    Asked once · last asked Aug 4 · Concept · Junior

88. What is the STP root bridge, and what role does it play in a network?

    Asked once · last asked Sep 18 · Concept · Junior

89. What are the various Wi‑Fi protocols?

    Asked once · last asked Sep 21 · Concept · Junior

90. What does a hardwired Internet connection mean?

    Asked once · last asked Sep 24 · Concept · Junior

91. How do you configure a LAN port?

    Asked once · last asked Oct 21 · Tooling · Junior

92. How do you configure a Cisco access point, and how do you install an operating system?

    Asked once · last asked Oct 21 · Tooling · Mid-level

93. What is Wi-Fi 7?

    Asked once · last asked Oct 22 · Concept · Junior

94. Does Wi-Fi 7 operate in the 6 GHz band?

    Asked once · last asked Oct 22 · Concept · Junior

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How this list is made

Every question here was asked by a real interviewer in a real job interview that a candidate ran MeetAssist in. After the call, the interviewer's questions are pulled from the transcript. Practice sessions, tests, exams and anything that was not a job interview are dropped.

Questions are rewritten so they make sense on their own: names of people, employers and clients are removed, and speech-to-text mistakes are fixed. Small talk, logistics and questions about one candidate's own résumé are left out. Rephrasings of the same question are merged, and the count is the number of different interviews it came up in.

The interviews come from candidates who use MeetAssist, so they lean towards software, data and AI roles: the shares describe these interviews, not every Computer Networks interview. Answers to the most asked questions are written and checked by an editor; a "common mistake" is shown only when reviews of real answers in these interviews show it, with the count.

337 interviews, 208 candidates, Nov 2025 to Oct 2026. Updated every month with new interviews.