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Objective 2.3XK0-005

2.3 Given 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.

2-3SecurityModerate

A packet traverses an entire iptables chain and matches no rule. What decides its fate?

The most recent rule addedRule recency has no special standing after a full traversal.
The kernel's routing tableRouting decides where a packet goes, not whether filtering accepts it.
The chain's policy targetCorrect · your answerCorrect. The chain policy decides unmatched packets.
An implicit ACCEPT at the endNo implicit ACCEPT exists; the policy is explicit.

Correct.

Concept

Built-in chains carry a default verdict for the unmatched case, which is where a default-deny stance is actually implemented.

Why C

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

#firewall#iptables

Now you: objective 2.3 questions

No account needed. The explanation opens when you answer.

Sample question 1 of 2

2-3SecurityModerate

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 2

2-3SecurityHard

A blocking rule must take effect before an existing accept rule at position one of the INPUT chain. Which command form places it there?

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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.

More objectives in Security