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300-410 Practice Question: Runs the following command to troubleshoot an…

A network engineer runs the following command to troubleshoot an IPv4 Access Control Lists issue:

R1# show ip access-lists 160

Extended IP access list 160

10 permit tcp 10.0.0.0 0.255.255.255 any eq 22
    
20 permit tcp 172.16.0.0 0.15.255.255 any eq 22
    
30 permit tcp 192.168.0.0 0.0.255.255 any eq 22
    
40 deny ip any any

What does this output indicate?

⚠ Common exam trap

Cisco often tests the distinction between 'permit all traffic' and 'permit specific traffic (e.g., SSH only)', leading candidates to overlook the port-specific 'eq 22' and incorrectly assume the ACL permits all traffic from the private ranges.

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

✓

The ACL permits SSH from private IP ranges and denies all other traffic.

The ACL permits TCP traffic to destination port 22 (SSH) from the three private IP ranges (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16) using wildcard masks that match the respective network prefixes. The final explicit deny ip any any statement blocks all other traffic, so only SSH from private IP ranges is permitted.

Answer analysis

Option-by-option breakdown

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

  • ✓

    The ACL permits SSH from private IP ranges and denies all other traffic.

    Why this is correct

    The wildcard masks 0.255.255.255, 0.15.255.255 and 0.0.255.255 match the 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 private ranges respectively, each permitting only TCP port 22. The trailing deny ip any any then drops every remaining packet, satisfying the implicit-deny requirement explicitly.

  • ✗

    The ACL permits all traffic from private IP ranges.

    Why it's wrong here

    Each permit statement matches TCP only, with destination port 22 (SSH), so HTTP, ICMP and other protocols from those ranges are denied by the final entry. It is tempting because the source addresses are RFC 1918 ranges, but the protocol and port conditions restrict what is actually permitted.

  • ✗

    The ACL denies SSH from private IP ranges.

    Why it's wrong here

    The ACL permits SSH from those private ranges and denies everything else; it does not deny SSH from them. It is tempting because the final deny ip any any looks like a blanket block, but statements 10 to 30 match first and permit TCP port 22.

  • ✗

    The ACL is applied inbound on an interface and is blocking all traffic.

    Why it's wrong here

    The output shows only the ACL's contents, not where it is applied or whether it is filtering live traffic; no interface binding appears. It is tempting because a trailing deny ip any any does drop unmatched packets, but that would require the ACL to be applied inbound on an interface.

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 300-410 practice question is part of Courseiva's free Cisco 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 300-410 exam.