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CAS-004 Extended ACL Practice Question

Exhibit

Refer to the exhibit.
```
access-list 101 deny ip any 10.0.0.0 0.0.0.255
```

Refer to the exhibit. Which of the following best describes the effect of this ACL?

⚠ Common exam trap

The CAS-004 exam often tests the distinction between source and destination in ACLs. Here, the trap is that candidates may think the ACL filters based on the source IP (like a standard ACL) and incorrectly choose an option about blocking traffic 'from' the network. However, this is an extended ACL with 'any' as source and the network as destination, so it blocks traffic 'to' the network.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

Blocks all traffic to the 10.0.0.0/24 network.

The ACL 'deny ip any 10.0.0.0 0.0.0.255' is an extended IP access-list that filters based on both source and destination. The source is 'any', meaning all sources, and the destination is the 10.0.0.0/24 network. Therefore, this ACL blocks all IP traffic destined to the 10.0.0.0/24 network, regardless of the source. The correct answer is that it blocks traffic to that network.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Blocks all traffic to the 10.0.0.0/24 network.

    Why this is correct

    The 'deny ip any 10.0.0.0 0.0.0.255' denies any source IP to destination network 10.0.0.0/24.

  • Blocks all traffic from the 10.0.0.0/24 network.

    Why it's wrong here

    The ACL denies traffic to the destination network, not from.

  • Permits all traffic to the 10.0.0.0/24 network.

    Why it's wrong here

    The ACL is a deny statement, not permit.

  • Permits all traffic from the 10.0.0.0/24 network.

    Why it's wrong here

    The ACL does not permit; it denies.

Visual reference

Source Router + ACL permit 10.0.0.0/8 deny any Server 10.0.0.5 ✓ 192.168.1.1 ✗ dropped ACLs evaluate top-down; first match wins — implicit deny all at end

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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This CAS-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CAS-005 exam.