When running Nginx behind Varnish with non-standard ports (e.g., Varnish on 80, Nginx on 8000), you might encounter unwanted port changes in redirects. For example, accessing example.com/blog might redirect to example.com:8000/blog/ instead of maintaining the original port 80.

This happens because Nginx's server_name_in_redirect and port_in_redirect directives default to using the actual listening port (8000) rather than the client-facing port (80). We need to make Nginx aware of the public-facing port.

Add these directives to your Nginx server block:

server {
    listen 8000;
    server_name example.com;
    
    # Fix redirect port issues
    port_in_redirect off;
    server_name_in_redirect off;
    absolute_redirect off;
    
    # Alternative if above doesn't work
    # proxy_set_header Host $host;
    # proxy_set_header X-Forwarded-Port 80;
    
    location / {
        # Your regular configuration
        try_files $uri $uri/ =404;
    }
}

After applying these changes, test with:

curl -I http://example.com/blog

Should return a Location header without port 8000:

HTTP/1.1 301 Moved Permanently
Location: http://example.com/blog/

If you're passing requests through Varnish with proxy headers, ensure proper header forwarding:

proxy_set_header Host $host;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-Port 80;

• Forgetting to reload Nginx (nginx -s reload)
• Multiple server blocks conflicting with each other
• Cache not being cleared between tests

The solution maintains clean URLs while preserving your reverse proxy architecture. Remember to test different scenarios including trailing slashes, missing files, and directory access.

# Bad redirect example
curl -I http://example.com/2023
HTTP/1.1 301 Moved Permanently
Location: http://example.com:8000/2023/

server {
    listen 8000;
    server_name example.com;
    
    # Critical settings for proper redirects
    port_in_redirect off;
    absolute_redirect off;
    
    # Alternative if you need absolute redirects
    # absolute_redirect on;
    # server_name_in_redirect on;
    
    location / {
        try_files $uri $uri/ =404;
    }
}

server {
    listen 8000;
    
    set $real_scheme $scheme;
    if ($http_x_forwarded_proto) {
        set $real_scheme $http_x_forwarded_proto;
    }
    
    set $real_port 80;
    if ($http_x_forwarded_port) {
        set $real_port $http_x_forwarded_port;
    }
    
    port_in_redirect off;
    absolute_redirect on;
    server_name_in_redirect on;
}

# Should return 301 without port 8000
curl -I http://example.com/blog

# Should maintain your domain without backend port
curl -I http://example.com/2023/