A SysOps administrator is troubleshooting an Amazon EC2 instance that is unreachable. The instance passes the system status check but fails the instance status check. Which TWO of the following are likely causes of this issue? (Choose TWO.)
A misconfigured firewall or iptables ruleset can block all inbound and outbound traffic, effectively making the instance unreachable despite the OS running normally. The instance status check performs a network reachability test at the OS level, and if the packet filtering rules prevent the response, the check fails, indicating an instance-level problem. Since the issue stems from guest OS configuration rather than AWS infrastructure, it is correctly identified as an instance status check failure.
Why this answer
An instance status check failure indicates that the operating system or the instance itself is not functioning correctly, even though the underlying hardware (system status check) is healthy. A misconfigured firewall or iptables can block required network traffic, causing the instance to appear unreachable, while a corrupted file system can prevent the OS from booting or operating properly, both of which are detected by the instance status check.
Exam trap
The trap here is that candidates often confuse instance status checks with system status checks, incorrectly attributing network-level issues (like detached volumes or external connectivity) to instance status failures when they actually belong to system status failures.