Top IT Support Engineer Interview Guide: 20 Must-Know Questions, Answers & Troubleshooting Scenarios

🔹 Basic Technical | IT Support Engineer interview preparation

1. What is an IP address? IPv4 vs IPv6

IP address: A unique identifier assigned to each device on a network for communication.
IPv4: 32-bit, written as four octets (e.g., 192.168.1.10), supports ~4.3 billion addresses.
IPv6: 128-bit, written in hexadecimal (e.g., 2001:0db8::1), supports a vastly larger address space and better security & efficiency.

2. What is DNS and DHCP?

DNS (Domain Name System): Translates domain names (like google.com) into IP addresses.
DHCP (Dynamic Host Configuration Protocol): Automatically assigns IP addresses and network settings (gateway, DNS) to devices on a network.

Top IT Support Engineer Interview Guide: 20 Must-Know Questions, Answers & Troubleshooting Scenarios

3. Difference between Switch, Router, and Hub

Device	Function	Layer
Hub	Broadcasts data to all ports	Physical Layer (Layer 1)
Switch	Forwards data to specific MAC addresses	Data Link Layer (Layer 2)
Router	Routes data between different networks	Network Layer (Layer 3)

4. What is a Firewall?

A Firewall is a security device (hardware/software) that monitors and filters incoming/outgoing network traffic based on defined security rules — it blocks unauthorized access while allowing legitimate communication.

🔹 Troubleshooting

1. PC connected to WiFi but no Internet – how to solve

Check if other devices can access the Internet.
Run ipconfig → see if a valid IP is assigned.
Restart router/WiFi adapter.
Try ping 8.8.8.8 (to test connectivity) and ping google.com (to test DNS).
Flush DNS: ipconfig /flushdns.
Check proxy or firewall settings.

2. Printer is connected but not printing – possible causes

Printer offline or wrong printer selected.
Paper jam / low ink / toner.
Print spooler service stopped → restart via Services.msc.
Driver issue → reinstall printer drivers.
Connection issue (USB/WiFi/network).

3. LAN cable connected but no network access – troubleshooting steps

Check link lights on NIC and switch.
Use ipconfig to verify IP.
Try a different cable/port.
Test static IP vs DHCP.
Check network adapter settings & drivers.
Disable/enable NIC or reboot system.

🔹 OS Related

1. What is Safe Mode in Windows?

Safe Mode starts Windows with minimum drivers and services — used for diagnosing driver/software issues or malware removal.

2. Common CMD Commands

Command	Function
ipconfig	Displays IP configuration
ping <host>	Tests connectivity
tracert <host>	Traces route to destination
nslookup <domain>	Checks DNS resolution
netstat	Shows active connections

3. Linux Commands for Network Connectivity

Command	Function
ifconfig or ip addr	Show IP configuration
ping <host>	Test connectivity
traceroute <host>	Trace network path
nslookup or dig	DNS check
netstat -rn	Routing table

🔹 Hardware & Software

1. Identifying RAM, HDD, or Power Supply issues

RAM: Frequent BSODs, random restarts, memory test failures.
HDD: Slow performance, clicking sounds, SMART errors, boot failures.
PSU: No power, random shutdowns, fan not spinning, burnt smell.

2. What happens if CMOS battery dies?

BIOS settings (time/date, boot order) reset to default.
System clock resets on reboot.
Replace the CMOS battery (CR2032) to fix.

🔹 Scenario Based

1. 10 users complain of slow Internet – how would you handle?

Check if issue is local or network-wide.
Test Internet speed on one machine.
Check switch/router utilization.
Identify bandwidth hogs or background downloads.
Restart network equipment.
Escalate to ISP if external issue.

2. How do you provide remote IT support?

Use tools like TeamViewer, AnyDesk, Remote Desktop (RDP), or SSH.
Verify user permission and obtain consent.
Diagnose via remote session, run commands, check logs.
Document issue and resolution for tracking.

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💼 Top 20 IT Support Engineer Interview FAQs (with Answers)

1. What is an IP address and how does it work?

An IP address uniquely identifies a device on a network. It helps route data between devices using the TCP/IP protocol.

IPv4: 32-bit (e.g., 192.168.1.10)
IPv6: 128-bit (e.g., 2001:0db8::1) — provides more address space and better security.

2. What is the difference between DNS and DHCP?

DNS (Domain Name System): Translates domain names into IP addresses.
DHCP (Dynamic Host Configuration Protocol): Automatically assigns IPs, subnet masks, and gateway information to devices.

3. What is the difference between a Switch, Router, and Hub?

Device	Function	Layer
Hub	Broadcasts to all devices	Layer 1
Switch	Connects devices within the same LAN using MAC addresses	Layer 2
Router	Connects multiple networks and routes traffic based on IP	Layer 3

4. What is a Firewall and why is it important?

A firewall monitors and controls network traffic based on security rules — it prevents unauthorized access and helps block malware and cyberattacks.

5. Your PC is connected to Wi-Fi but has no Internet. How do you troubleshoot?

Check other devices – network-wide or device-specific issue.
Run ipconfig /all to verify IP address.
Try ping 8.8.8.8 (connectivity) and ping google.com (DNS).
Restart router/Wi-Fi adapter.
Flush DNS (ipconfig /flushdns).
Check proxy/firewall settings.

Top IT Support Engineer Interview Guide: 20 Must-Know Questions, Answers & Troubleshooting Scenarios

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6. Printer is connected but not printing. What could be wrong?

Wrong default printer selected.
Printer spooler service stopped.
Paper jam, low ink/toner.
USB/network connectivity issue.
Driver needs reinstalling.

7. What are the steps to troubleshoot a LAN cable connection with no network access?

Check physical connections and port LEDs.
Run ipconfig to verify IP.
Try another cable or switch port.
Disable/enable network adapter.
Update network driver.
Test with static IP.

8. What is Safe Mode in Windows and when is it used?

Safe Mode starts Windows with minimal drivers and services.
Used to fix driver conflicts, remove malware, or troubleshoot startup issues.

9. What are some common CMD commands used in networking?

Command	Purpose
ipconfig	Shows network configuration
ping <host>	Tests connectivity
tracert <host>	Traces route to destination
nslookup <domain>	Tests DNS resolution
netstat	Displays active connections

10. Which Linux commands help check network connectivity?

ifconfig / ip addr → View IPs
ping → Test connectivity
traceroute → Show path
dig / nslookup → DNS info
netstat -rn → Routing table

11. How do you identify RAM, HDD, or PSU issues in a computer?

RAM: Frequent restarts or BSOD → Run Windows Memory Diagnostic.
HDD: Clicking noise, slow access → Use CHKDSK or SMART test.
PSU: PC won’t power on, random shutdowns → Test with multimeter or PSU tester.

12. What happens when the CMOS battery fails?

The BIOS settings (time/date, boot order) reset to defaults every time the PC restarts. Replace the CR2032 CMOS battery to fix it.

13. Ten users report slow Internet. What’s your first step?

Check if it’s local or network-wide.
Run speed test from multiple PCs.
Check router/switch utilization.
Look for large downloads or streaming.
Restart networking equipment.
Escalate to ISP if external issue.

14. How do you provide remote IT support?

Use tools like TeamViewer, AnyDesk, or Remote Desktop.

Authenticate and gain user consent.
Diagnose and fix remotely.
Document the issue and solution.

15. What is Active Directory (AD)?

Active Directory is Microsoft’s directory service for managing users, computers, and resources in a Windows domain environment — supports authentication, authorization, and group policies.

16. What is the difference between TCP and UDP?

Protocol	TCP	UDP
Type	Connection-oriented	Connectionless
Reliability	Reliable (acknowledgements)	Unreliable
Speed	Slower	Faster
Examples	HTTP, FTP	DNS, VoIP

17. How do you reset a forgotten Windows admin password?

Boot from a recovery disk → open Command Prompt.
Use net user command to reset password.
Or use third-party password recovery tools (with permission).

18. How do you check system performance issues in Windows?

Task Manager: Check CPU, RAM, disk usage.
Resource Monitor: Analyze processes.
Event Viewer: Check for system errors.
Disk Cleanup / Defragmenter: Free space and optimize.

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19. What steps would you take if a user reports email not working?

Verify Internet connection.
Check server settings (IMAP/SMTP).
Restart Outlook or mail app.
Check mailbox size / quota.
Verify credentials or reset password.

20. Why do you want to work as an IT Support Engineer?

Sample Answer:
“I enjoy solving technical problems and helping users work efficiently. IT support lets me combine my technical knowledge with communication skills to provide fast, reliable solutions and keep systems running smoothly.”

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