IIS 10.0 Interview Questions and Answers (25 Questions)

These questions are suitable for Windows Server Administrator, System Administrator, DevOps Engineer, and IIS Administrator interviews.

1. What is IIS?

Answer:
IIS (Internet Information Services) is Microsoft's web server software used to host websites, web applications, REST APIs, FTP sites, and web services on Windows operating systems.

2. What are the main features of IIS 10?

Answer:

• HTTP/2 support

• HTTPS with SSL/TLS

• Application Pools

• Request Filtering

• URL Rewrite

• Logging and Monitoring

• FTP Server

• Windows Authentication

• Compression

• PowerShell Management

3. What is an Application Pool?

Answer:
An Application Pool is a logical container that isolates one or more web applications. Each Application Pool runs independently, improving security, stability, and performance.

Benefits

• Process isolation

• Fault isolation

• Independent recycling

• Separate security identity

4. What is w3wp.exe?

Answer:
w3wp.exe is the IIS Worker Process responsible for processing HTTP requests for websites running in an Application Pool.

5. What is the default IIS website location?

Answer:

C:\inetpub\wwwroot

6. Which ports are used by IIS?

Answer:

7. What is a Website Binding?

Answer:
Binding connects a website with:

• IP Address

• Port Number

• Host Name

• SSL Certificate (for HTTPS)

Example:

https://company.com:443

8. What is Host Header?

Answer:
Host Header allows multiple websites to run on the same server using the same IP address and port but different domain names.

Example:

www.company.com
portal.company.com
mail.company.com

9. What is an Application Pool Identity?

Answer:
Application Pool Identity is the Windows account used by the worker process.

Common identities:

• ApplicationPoolIdentity (Default)

• LocalSystem

• LocalService

• NetworkService

• Custom Domain Account

10. What is Recycling in IIS?

Answer:
Recycling restarts the Worker Process without restarting the entire IIS service.

Reasons:

• Free memory

• Remove memory leaks

• Improve performance

• Scheduled maintenance

11. Difference between IISRESET and Recycling?

Answer:

12. What is Web.config?

Answer:
Web.config is an XML configuration file used to configure an ASP.NET application.

Example settings:

• Authentication

• Authorization

• Connection strings

• Custom errors

• URL Rewrite

13. What is HTTP.sys?

Answer:
HTTP.sys is a kernel-mode driver that listens for HTTP requests before passing them to IIS Worker Processes.

Advantages:

• Better performance

• Request queuing

• SSL handling

• Kernel-mode caching

14. What is Request Filtering?

Answer:
Request Filtering protects the server by blocking malicious requests.

Examples:

• Block file extensions

• Block HTTP verbs

• Limit request size

• Prevent directory traversal attacks

15. What are IIS Logs?

Answer:
IIS logs record website activity.

Information includes:

• Client IP

• Date & Time

• URL

• Status Code

• User Agent

• Bytes Sent

Default Location:

C:\inetpub\logs\LogFiles

16. What are HTTP Status Codes?

Answer:

17. Difference between 401 and 403?

Answer:

401 Unauthorized

• Authentication required.

• User has not logged in or credentials are invalid.

403 Forbidden

• User is authenticated but does not have permission.

18. What is Anonymous Authentication?

Answer:
Anonymous Authentication allows users to access a website without providing credentials.

Used for:

• Public websites

• Company homepages

• Informational sites

19. What is Windows Authentication?

Answer:
Windows Authentication uses Active Directory credentials.

Commonly used for:

• Internal company portals

• SharePoint

• Intranet applications

20. How do you secure an IIS website?

Answer:

• Enable HTTPS

• Install SSL Certificate

• Disable unused modules

• Enable Request Filtering

• Use least-privilege Application Pool identities

• Keep Windows and IIS updated

• Enable logging and monitoring

• Restrict administrative access

21. How do you troubleshoot a website that returns HTTP 503?

Answer:
Common causes:

• Application Pool stopped

• Worker process crashed

• Application Pool identity password expired

• Resource exhaustion

Steps:

1. Check Application Pool status.

2. Review Event Viewer.

3. Examine IIS logs.

4. Restart the Application Pool.

5. Verify application configuration.

22. How do you deploy an ASP.NET application to IIS?

Answer:

1. Publish the application from Visual Studio or dotnet publish.

2. Copy the published files to the web root.

3. Create a website or application in IIS.

4. Assign an Application Pool.

5. Configure bindings.

6. Set folder permissions.

7. Browse and test the site.

23. What is URL Rewrite?

Answer:
URL Rewrite changes incoming URLs without changing the application's internal structure.

Examples:

• Redirect HTTP to HTTPS

• Redirect old URLs to new ones

• Create SEO-friendly URLs

• Force www or non-www

24. What is Failed Request Tracing (FREB)?

Answer:
Failed Request Tracing captures detailed information about requests that fail or take too long.

It helps diagnose:

• 404 errors

• 500 errors

• Slow requests

• Module execution issues

• Authentication problems

25. Explain the IIS Request Processing Architecture.

Answer:

Client Browser
       │
       ▼
HTTP/HTTPS Request
       │
       ▼
HTTP.sys
       │
       ▼
Application Pool
       │
       ▼
Worker Process (w3wp.exe)
       │
       ▼
ASP.NET/.NET Runtime
       │
       ▼
Website/Application
       │
       ▼
Database/File System
       │
       ▼
Response to Client

Flow Explanation:

1. The browser sends an HTTP/HTTPS request.

2. HTTP.sys receives the request and queues it.

3. The request is routed to the appropriate Application Pool based on the site binding.

4. The w3wp.exe worker process processes the request.

5. The application executes any required business logic and may query a database or read files.

6. IIS returns the generated response to the client.

Bonus Rapid-Fire Interview Questions

1. What is IIS Manager?

2. What is a Virtual Directory?

3. What is an IIS Module?

4. What is an IIS Handler?

5. How do you enable HTTPS in IIS?

6. What is the difference between a Website and an Application in IIS?

7. Where are IIS logs stored?

8. How do you restart an Application Pool?

9. What causes a 500 Internal Server Error?

10. What is the purpose of applicationHost.config?

These questions cover the concepts and troubleshooting scenarios that are commonly asked in interviews for IIS 10.0 administration and support roles.