Objective 2.3
XK0-005Given a scenario, implement and configure firewalls.
Objective 2.3 sits in Security, which carries 21% of the Linux+ exam. The questions below are original, written from the official objective title above, and each explanation cites the CompTIA page it rests on.
Objective title verbatim from the official objectives. CompTIA exam page ↗
A worked example
Shown solved, with the whole explanation open: this is what every question here carries.
A packet traverses an entire iptables chain and matches no rule. What decides its fate?
Correct.
Checked against man7.org, August 2026Concept
Built-in chains carry a default verdict for the unmatched case, which is where a default-deny stance is actually implemented.
Why B
When no rule matches, the target specified by the chain policy determines the fate of the packet, which is why hardening sets the policy itself.
Source
iptables(8), packet filtering administration, checked August 2026…ched, the target specified by the chain policy determines the fate of the packet.
Now you: objective 2.3 questions
No account needed. The explanation opens when you answer.
Sample question 1 of 3
A firewall change must make unmatched inbound packets vanish with no response to the sender. Which target does that when set as policy?
Sample question 2 of 3
A blocking rule must take effect before an existing accept rule at position one of the INPUT chain. Which command form places it there?
Sample question 3 of 3
An administrator adds a firewalld rule with --permanent, but it is not active and a reboot is not an option. What completes the change?
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Read the sources
These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.