Question 1,328 of 2,152
Control Plane Policing (CoPP)mediumMultiple ChoiceObjective-mapped

CoPP ACL Configuration for OSPF, BGP, and LDP

This 300-410 practice question tests your understanding of control plane policing (copp). This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.

Analyze the following partial configuration:

access-list 101 permit tcp any any eq 179
access-list 
101 permit udp any any eq 646
access-list 
101 permit ospf any any

! class-map match-all COPP-BGP match access-group 101 ! policy-map COPP-POLICY

class COPP-BGP

police 48000 conform-action transmit exceed-action drop

class class-default

police 128000 conform-action transmit exceed-action drop !

interface GigabitEthernet0/0
 ip address 192.168.1.1 255.255.255.0

! control-plane service-policy input COPP-POLICY

Which statement is true?

Quick Answer

The answer is that the ACL matches OSPF, BGP, and LDP traffic, and all are rate-limited to 48000 bps. This is correct because the access-list 101 explicitly permits OSPF (protocol 89), BGP (TCP port 179), and LDP (UDP port 646), and the class-map COPP-BGP matches all three protocols, applying a single policer of 48000 bps via the policy-map. On the Cisco CCNP ENARSI 300-410 exam, CoPP ACL configuration for OSPF, BGP, and LDP tests your ability to identify which control-plane protocols are being protected and whether the policing rate is appropriate; a common trap is assuming each protocol gets its own policer when they are grouped under one class. Remember that LDP uses UDP port 646, not TCP, and BGP uses TCP port 179—a quick memory tip is “BGP is TCP, LDP is UDP, OSPF is its own protocol number 89.”

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 matches OSPF, BGP, and LDP traffic, and all are rate-limited to 48000 bps.

Option A is correct because the ACL permits TCP port 179 (BGP), UDP port 646 (LDP), and OSPF (protocol 89). The class-map COPP-BGP matches all three protocols via the match-all keyword, and the policy-map applies a police rate of 48000 bps to this class. Since the policy is applied to the control-plane input, all matched traffic (BGP, LDP, OSPF) is rate-limited to 48000 bps.

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 matches OSPF, BGP, and LDP traffic, and all are rate-limited to 48000 bps.

    Why this is correct

    Correct. The ACL permits OSPF (protocol 89), BGP (TCP 179), and LDP (UDP 646). The class-map matches all three and applies the 48000 bps policer.

    Related concept

    Read the scenario before looking for a memorised answer.

  • The ACL is missing 'permit eigrp any any' to include EIGRP traffic.

    Why it's wrong here

    Incorrect. EIGRP is not required; the configuration is valid as is.

  • The class-map must use 'match-all' to match all protocols simultaneously, but the ACL uses 'permit' which is OR logic, so the class-map will not work.

    Why it's wrong here

    Incorrect. The ACL uses permit statements with OR logic; the class-map match-all means all match conditions must be met, but since there is only one match condition (the ACL), it works fine.

  • The policy-map should be applied to the interface, not the control-plane.

    Why it's wrong here

    Incorrect. CoPP is applied to the control-plane, not to interfaces. Interface-level policing would be different.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that 'match-all' in a class-map requires all protocols in the ACL to be matched simultaneously, but in reality, 'match-all' applies to the match statements within the class-map, not to the individual entries within the referenced ACL.

Detailed technical explanation

How to think about this question

Control Plane Policing (CoPP) uses a policy-map applied to the control-plane to rate-limit traffic destined to the router's CPU, protecting it from overwhelming control-plane protocols. The ACL in this configuration matches BGP (TCP 179), LDP (UDP 646), and OSPF (protocol 89), which are all critical routing protocols; the police rate of 48000 bps (48 kbps) is a relatively low rate, often used in lab or low-bandwidth scenarios. In real-world deployments, CoPP is essential for mitigating control-plane attacks, and the police rate must be carefully tuned to avoid dropping legitimate protocol traffic.

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 network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.

Visual reference

R1 R2 R3 R4 10 100 10 100 OSPF picks R1→R2→R4 (cost 20) over R1→R3→R4 (cost 200)

Quick reference

Routing Protocol Comparison

ProtocolMetricMax HopsAlgorithmType
RIP v2Hop count15Bellman-FordDistance vector
OSPFCost (bandwidth)UnlimitedDijkstra (SPF)Link state
EIGRPComposite metricUnlimitedDUALHybrid
IS-ISCostUnlimitedDijkstraLink state
BGPPolicy / attributesUnlimitedPath vectorPath vector

RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.

What to study next

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FAQ

Questions learners often ask

What does this 300-410 question test?

Control Plane Policing (CoPP) — This question tests Control Plane Policing (CoPP) — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The ACL matches OSPF, BGP, and LDP traffic, and all are rate-limited to 48000 bps. — Option A is correct because the ACL permits TCP port 179 (BGP), UDP port 646 (LDP), and OSPF (protocol 89). The class-map COPP-BGP matches all three protocols via the match-all keyword, and the policy-map applies a police rate of 48000 bps to this class. Since the policy is applied to the control-plane input, all matched traffic (BGP, LDP, OSPF) is rate-limited to 48000 bps.

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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Last reviewed: Jul 4, 2026

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