This 300-410 practice question tests your understanding of mpls operations. 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.
CoPP (Control Plane Policing) rate-limit impacts legitimate traffic. Router R1 has CoPP policy applied: 'class-map match-all BGP class-map match-all SSH match protocol bgp match protocol ssh policy-map COPP class BGP police 10000 conform-action transmit exceed-action drop'. Network engineers cannot SSH to R1, but BGP sessions are stable. 'show policy-map control-plane' output shows 'BGP class: 0 packets, 0 bytes' and 'SSH class: 0 packets, 0 bytes'. 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 class-map uses 'match-all' instead of 'match-any', causing SSH traffic not to match the class and be dropped by default action.
The class-map uses 'match protocol bgp' and 'match protocol ssh' with match-all, meaning both conditions must be true for a packet to match. SSH packets do not match protocol bgp, so they fall through to the default class, which may have a drop policy. The class-map should be match-any or separate classes for each protocol.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 class-map uses 'match-all' instead of 'match-any', causing SSH traffic not to match the class and be dropped by default action.
Why this is correct
With match-all, a packet must be both BGP and SSH, which is impossible; SSH packets go to default class, likely drop.
Related concept
Standard ACLs match source addresses.
✗
The police rate is too low for SSH traffic; need to increase.
Why it's wrong here
No packets matched, so rate is irrelevant.
✗
ACL on the interface blocks SSH before CoPP is applied.
CoPP is applied to the wrong direction; should be input.
Why it's wrong here
CoPP is typically applied to control-plane input.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related 300-410 ACL questions on filtering logic and placement.
MPLS Operations — This question tests MPLS Operations — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The class-map uses 'match-all' instead of 'match-any', causing SSH traffic not to match the class and be dropped by default action. — The class-map uses 'match protocol bgp' and 'match protocol ssh' with match-all, meaning both conditions must be true for a packet to match. SSH packets do not match protocol bgp, so they fall through to the default class, which may have a drop policy. The class-map should be match-any or separate classes for each protocol.
What should I do if I get this 300-410 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related 300-410 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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