Question 702 of 2,015

ACLs and CoPP →hardMultiple SelectObjective-mapped

Quick Answer

The answer is that CoPP can rate-limit ICMP packets destined to the router by using an ACL to match ICMP in the class-map. This is correct because ACLs serve as the classification mechanism within a CoPP policy, identifying specific control-plane traffic—such as ICMP, SSH, or BGP—by matching packet headers before the router applies a policing action. On the ENCOR 350-401 exam, this concept tests your understanding that CoPP uses ACLs to filter traffic destined for the control plane, not transit traffic, and that the class-map defines the match criteria while the policy-map enforces the rate-limit. A common trap is confusing the order of processing: ACLs are applied inside the class-map, not before CoPP, and CoPP does not inspect data-plane forwarding. Remember the mnemonic "ACL in Class, Police in Policy" to keep the hierarchy straight.

350-401 ACLs and CoPP Practice Question

This 350-401 practice question tests your understanding of acls and copp. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.

Which two statements about the interaction between ACLs and CoPP are true? (Choose two.)

Question 1hardmulti select

Study the full ACL explanation →

A
ACLs are used in CoPP class-maps to match specific control-plane traffic types.
Correct because CoPP uses class-maps that reference ACLs to identify traffic such as SSH, SNMP, or routing protocol packets.
B
CoPP can rate-limit ICMP packets destined to the router by using an ACL to match ICMP in the class-map.
Correct because an ACL can match ICMP traffic, and CoPP can apply a police action to limit its rate to the control plane.
C
ACLs applied to interfaces take precedence over CoPP policies for control-plane traffic.
Why wrong: Incorrect because CoPP is applied to the control plane itself; interface ACLs affect traffic before it reaches the control plane, but CoPP is the final arbiter for control-plane-bound packets.
D
CoPP can only use extended ACLs, not standard ACLs, for classification.
Why wrong: Incorrect because CoPP can use both standard and extended ACLs, though extended ACLs are more common for granularity.
E
CoPP policies are applied globally and affect all traffic entering the router, including transit traffic.
Why wrong: Incorrect because CoPP only affects traffic destined to the control plane, not transit traffic.

Full breakdown with real-world context →

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

✓

ACLs are used in CoPP class-maps to match specific control-plane traffic types.

ACLs are used within CoPP to classify control-plane traffic. CoPP can protect against DoS attacks, and ACLs provide the classification. The incorrect options misstate the order of processing or the scope of CoPP.

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.

✓
ACLs are used in CoPP class-maps to match specific control-plane traffic types.
Why this is correct
Correct because CoPP uses class-maps that reference ACLs to identify traffic such as SSH, SNMP, or routing protocol packets.
Related concept
Standard ACLs match source addresses.
✓
CoPP can rate-limit ICMP packets destined to the router by using an ACL to match ICMP in the class-map.
Why this is correct
Correct because an ACL can match ICMP traffic, and CoPP can apply a police action to limit its rate to the control plane.
Related concept
Standard ACLs match source addresses.
✗
ACLs applied to interfaces take precedence over CoPP policies for control-plane traffic.
Why it's wrong here
Incorrect because CoPP is applied to the control plane itself; interface ACLs affect traffic before it reaches the control plane, but CoPP is the final arbiter for control-plane-bound packets.
✗
CoPP can only use extended ACLs, not standard ACLs, for classification.
Why it's wrong here
Incorrect because CoPP can use both standard and extended ACLs, though extended ACLs are more common for granularity.
✗
CoPP policies are applied globally and affect all traffic entering the router, including transit traffic.
Why it's wrong here
Incorrect because CoPP only affects traffic destined to the control plane, not transit traffic.

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.

What to study next

Got this wrong? Here's your next step.

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 350-401 ACL questions on filtering logic and placement.

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FAQ

Questions learners often ask

What does this 350-401 question test?

ACLs and CoPP — This question tests ACLs and CoPP — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: ACLs are used in CoPP class-maps to match specific control-plane traffic types. — ACLs are used within CoPP to classify control-plane traffic. CoPP can protect against DoS attacks, and ACLs provide the classification. The incorrect options misstate the order of processing or the scope of CoPP.

What should I do if I get this 350-401 question wrong?

What is the key concept behind this question?

Standard ACLs match source addresses.

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