The answer is that the ACL order is causing the management traffic drop because the single deny statement in access-list 100 blocks all IP traffic, including SSH, before any permit statement can be evaluated. This is a classic example of how an implicit deny at the end of an access control list works, but here the explicit `deny ip any any log` immediately denies all packets, making the order of entries critical. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding that VTY ACLs filter inbound management traffic, and a common trap is forgetting to place a permit statement for the management protocol—like SSH on TCP port 22—before the deny. The root cause is not a misconfigured protocol but a sequencing error: the ACL processes top-down, so the deny hits first. Remember the mnemonic "Permit before you deny, or your SSH will cry."
300-410 IPv4 Access Control Lists Practice Question
This 300-410 practice question tests your understanding of ipv4 access control lists. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Management traffic is being dropped. Router R1 has: access-list 100 deny ip any any log, applied to VTY lines. Remote access via SSH fails, but console works. What is the root cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ACL should permit SSH before the deny statement.
The ACL `access-list 100 deny ip any any log` applied to VTY lines denies all IP traffic, including SSH, before any permit statement can match. Since SSH traffic is denied, remote access fails. The correct fix is to add a `permit tcp any any eq 22` statement before the deny to allow SSH management traffic.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 should permit SSH before the deny statement.
Why this is correct
Without a permit statement for SSH, the deny blocks all traffic.
Related concept
Read the scenario before looking for a memorised answer.
✗
The VTY lines require transport input ssh, but the ACL is irrelevant.
Why it's wrong here
Transport input controls protocol, but ACL filters traffic.
✗
The ACL is applied to the wrong interface.
Why it's wrong here
VTY ACL filters incoming Telnet/SSH; application is correct.
✗
The log keyword causes performance issues, not drops.
Why it's wrong here
Logging does not cause drops; the deny does.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think the ACL is applied to an interface (Option C) or that the `log` keyword causes the problem, when in fact the issue is the order of ACL entries—specifically, the missing permit for SSH before the global deny.
Detailed technical explanation
How to think about this question
Under the hood, VTY access-class filters are evaluated in order; the first matching entry determines the action. Since `deny ip any any` matches all IP traffic (including SSH), the router drops the SSH session before it can be established. A common real-world scenario is when an administrator locks themselves out by applying a restrictive ACL without first permitting their own management protocol (e.g., SSH, Telnet, SNMP).
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
IPv4 Access Control Lists — This question tests IPv4 Access Control Lists — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The ACL should permit SSH before the deny statement. — The ACL `access-list 100 deny ip any any log` applied to VTY lines denies all IP traffic, including SSH, before any permit statement can match. Since SSH traffic is denied, remote access fails. The correct fix is to add a `permit tcp any any eq 22` statement before the deny to allow SSH management traffic.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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