Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
What is the main purpose of an allowlist-based firewall policy compared with a denylist-based one?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
It allows all traffic except a few known bad flows.
That describes a denylist approach.
B
Best answer
It permits only explicitly approved traffic patterns.
Correct. Allowlist policies are restrictive by default.
C
Distractor review
It automatically encrypts all allowed traffic.
Filtering policy does not imply encryption.
D
Distractor review
It disables the implicit deny at the end of the ACL.
The implicit deny remains part of ACL logic.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is confusing allowlist-based firewall policies with denylist-based ones. Many candidates mistakenly think that allowlists allow all traffic except some bad flows, which actually describes a denylist approach. This confusion leads to incorrect answers because allowlists are restrictive by default, permitting only explicitly approved traffic and denying everything else. The implicit deny at the end of Cisco ACLs enforces this behavior, but candidates unfamiliar with this detail may overlook it. Understanding this distinction is crucial to avoid selecting the wrong option in CCNA Security Fundamentals questions.
Technical deep dive
How to think about this question
An allowlist-based firewall policy is a security approach that permits only explicitly approved traffic to pass through the firewall, blocking all other traffic by default. This method is inherently restrictive, ensuring that only known, trusted traffic patterns are allowed, which reduces the attack surface and limits exposure to unauthorized or malicious network flows. In Cisco networking and CCNA contexts, allowlists are often implemented using Access Control Lists (ACLs) or firewall rules that specify permitted IP addresses, protocols, and ports. The decision process behind an allowlist policy contrasts with a denylist policy, which permits all traffic except those explicitly blocked. The allowlist enforces a default deny stance, meaning any traffic not matching the approved criteria is automatically dropped. This approach aligns with the principle of least privilege, which is fundamental in network security design and is emphasized in Cisco's security fundamentals domain. The implicit deny at the end of ACLs supports this behavior by ensuring unmatched traffic is denied. A common exam trap is confusing allowlist policies with denylist policies. Candidates may incorrectly believe that allowlists permit all traffic except some bad flows, which is the opposite of their actual function. Practically, Cisco devices use ACLs with implicit deny to enforce allowlists, and understanding this default deny behavior is critical. In real-world networks, allowlists provide stronger security but require careful management to avoid inadvertently blocking legitimate traffic.
KKey Concepts to Remember
- An allowlist-based firewall policy permits only explicitly approved traffic patterns and denies all other traffic by default.
- A denylist-based firewall policy allows all traffic except for a few known bad flows that are explicitly blocked.
- Cisco Access Control Lists (ACLs) implement allowlist behavior by using an implicit deny at the end of the ACL to block unmatched traffic.
- The principle of least privilege underpins allowlist policies by restricting network access to only what is necessary and authorized.
- Allowlist policies reduce the attack surface by preventing unauthorized or unknown traffic from entering the network.
- Misunderstanding allowlist policies as permissive rather than restrictive is a common exam trap in the CCNA Security Fundamentals domain.
- Allowlist enforcement requires careful configuration to avoid blocking legitimate traffic while maintaining strict security controls.
- Cisco firewall and ACL configurations rely on explicit permit statements followed by an implicit deny to implement allowlist security effectively.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
An allowlist-based firewall policy permits only explicitly approved traffic patterns and denies all other traffic by default.
What is the correct answer to this question?
The correct answer is: It permits only explicitly approved traffic patterns. — An allowlist permits only explicitly approved traffic and denies everything else by default, which is generally more restrictive.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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