IPTables REJECT vs DROP: Deep Technical Differences, Real-World Behavior, and Best Practices

If you have tested open ports with netcat, checked disk usage with df and du, explored directories using the LS command, tweaked configs in vim, or upgraded to kernel 6.19.3, you’re already comfortable operating at a system level. The next natural step in mastering Linux infrastructure is understanding how your firewall actually behaves. And one of the most misunderstood details in firewall configuration is the difference between REJECT and DROP in iptables.