Default server handling in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What happens when a request matches no server_name?

Given this nginx configuration snippet:

server {
    listen 80 default_server;
    server_name _;
    return 200 'Default server response';
}

server {
    listen 80;
    server_name example.com;
    return 200 'Example.com response';
}

What will be the response body when a request is sent to IP address directly (no Host header or unknown Host)?

Nginx

server {
    listen 80 default_server;
    server_name _;
    return 200 'Default server response';
}

server {
    listen 80;
    server_name example.com;
    return 200 'Example.com response';
}

A The response body will be 'Default server response'

B The response body will be 'Example.com response'

C The request will be rejected with 404 Not Found

D The request will timeout with no response

💡 Hint

Think about which server block nginx uses when no server_name matches.

Nginx uses the server block marked with 'default_server' for requests that don't match any server_name. Here, the first server block is the default, so it responds with 'Default server response'.

❓ Configuration

intermediate

Identify the correct default server configuration

Which nginx server block configuration correctly sets a default server for HTTP port 80?

A

server {
    listen 80 default_server;
    server_name _;
    return 200 'Default';
}

B

server {
    listen 80;
    server_name default_server;
    return 200 'Default';
}

C

server {
    listen 80 default;
    server_name _;
    return 200 'Default';
}

D

server {
    listen 80 default_server on;
    server_name _;
    return 200 'Default';
}

💡 Hint

The 'default_server' keyword must be used with 'listen'.

Only option A uses the correct syntax 'listen 80 default_server;' to mark the server block as default. Other options have invalid syntax or misuse the directive.

❓ Troubleshoot

advanced

Why does nginx serve the wrong server block?

You have two server blocks:

server {
    listen 80 default_server;
    server_name example.com;
    return 200 'Example.com default';
}

server {
    listen 80;
    server_name test.com;
    return 200 'Test.com';
}

You send a request with Host header 'test.com' but nginx responds with 'Example.com default'. What is the likely cause?

A The first server block is default_server and matches all requests, ignoring server_name

B The second server block has a syntax error and is ignored

C Nginx does not support multiple server blocks on the same port

D The Host header is missing in the request, so default_server is used

💡 Hint

Check if the Host header is correctly sent in the request.

If the Host header is missing or incorrect, nginx cannot match server_name and falls back to the default_server block. This causes the default server block to respond even if another server_name matches.

🔀 Workflow

advanced

Order the steps to set a default server in nginx

Put these steps in the correct order to configure a default server for HTTP requests in nginx:

A 1,3,2,4

B 2,1,3,4

C 1,2,3,4

D 1,2,4,3

💡 Hint

Think about editing config, then reloading, then testing.

First edit the config, then add the default_server directive, reload nginx to apply, and finally test the setup.

✅ Best Practice

expert

Which is the best practice for default server handling in nginx?

Choose the best practice for configuring a default server in nginx to handle unmatched requests safely and clearly.

A Use multiple server blocks with the same server_name and rely on nginx to load balance between them

B Use a dedicated server block with 'listen 80 default_server;' and a generic server_name like '_' that returns a simple 444 or 404 response

C Set the first server block without default_server and rely on nginx to pick the first block as default

D Do not configure a default server; let nginx return 502 Bad Gateway for unmatched requests

💡 Hint

Think about clarity and security for unmatched requests.

Best practice is to explicitly define a default server block with 'default_server' and a generic server_name like '_'. It should return a minimal response like 444 (connection closed) or 404 to avoid leaking information or serving unintended content.