- A
EIGRP uses multicast, and CoPP cannot police multicast traffic.
Why wrong: CoPP can police any traffic destined to the control plane, including multicast.
- B
The police rate in pps is too low, causing EIGRP reliable packets (queries/replies) to be dropped, leading to SIA.
EIGRP's reliable transport requires all packets to be acknowledged; drops cause retransmissions and potential SIA.
- C
CoPP only affects incoming traffic, but EIGRP SIA is caused by outgoing packet drops.
Why wrong: CoPP affects incoming traffic to the control plane, which includes EIGRP packets from neighbors.
- D
EIGRP uses TCP, and CoPP only polices UDP.
Why wrong: EIGRP uses IP protocol 88, not TCP or UDP.
Question 2,097 of 2,152
CoPP EIGRP Stuck-in-Active — Reliable Transport Issues | Cisco CCNP ENARSI 300-410 Explained
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.
An engineer configures CoPP on a router running EIGRP. The policy includes a class-map matching EIGRP traffic with a police rate of 1000 pps. After applying the policy, EIGRP neighbors form but occasionally go active and become stuck-in-active (SIA). Which is the most likely explanation?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Quick Answer
The answer is that the police rate in pps is too low, causing EIGRP reliable packets to be dropped and leading to a stuck-in-active (SIA) condition. This occurs because EIGRP relies on its Reliable Transport Protocol (RTP) for critical messages like queries and replies during network convergence; when CoPP drops these packets, the querying router never receives an acknowledgment or reply, so it holds the route in active state until the SIA timer expires. On the Cisco CCNP ENARSI 300-410 exam, this question tests your understanding of how control-plane policing interacts with EIGRP’s reliable transport—a common trap is assuming any CoPP drop will break neighbor adjacency, but here neighbors form because hello packets (unreliable transport) still pass, while only the reliable query/reply exchange fails. A helpful memory tip: “Queries need replies, not just hellos—if CoPP clips the reliable, SIA will follow.”
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 police rate in pps is too low, causing EIGRP reliable packets (queries/replies) to be dropped, leading to SIA.
EIGRP uses RTP (Reliable Transport Protocol) for certain packets like queries and replies. These reliable packets require acknowledgment; if the CoPP police rate of 1000 pps is too low, EIGRP queries or replies may be dropped. Missing acknowledgments cause the neighbor to be declared active, and if the query process is not completed within the active timer, the route becomes stuck-in-active (SIA).
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.
- ✗
EIGRP uses multicast, and CoPP cannot police multicast traffic.
Why it's wrong here
CoPP can police any traffic destined to the control plane, including multicast.
- ✓
The police rate in pps is too low, causing EIGRP reliable packets (queries/replies) to be dropped, leading to SIA.
Why this is correct
EIGRP's reliable transport requires all packets to be acknowledged; drops cause retransmissions and potential SIA.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
CoPP only affects incoming traffic, but EIGRP SIA is caused by outgoing packet drops.
Why it's wrong here
CoPP affects incoming traffic to the control plane, which includes EIGRP packets from neighbors.
- ✗
EIGRP uses TCP, and CoPP only polices UDP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume CoPP only affects incoming traffic or that EIGRP uses TCP, but the key is understanding that EIGRP's reliable packets (queries/replies) are sensitive to drops, and a low pps police rate can cause SIA.
Detailed technical explanation
How to think about this question
EIGRP's RTP uses sequence numbers and retransmission timeouts for reliable delivery. When CoPP drops a query or reply packet, the sender does not receive an ACK and retransmits, but if the drop rate exceeds the retransmission threshold, the neighbor is placed in active state. If the query process is not completed within 3 minutes (default active timer), the route becomes SIA, often indicating that the police rate is insufficient for the volume of EIGRP control traffic during convergence events.
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.
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
What to study next
Got this wrong? Here's your next step.
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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 police rate in pps is too low, causing EIGRP reliable packets (queries/replies) to be dropped, leading to SIA. — EIGRP uses RTP (Reliable Transport Protocol) for certain packets like queries and replies. These reliable packets require acknowledgment; if the CoPP police rate of 1000 pps is too low, EIGRP queries or replies may be dropped. Missing acknowledgments cause the neighbor to be declared active, and if the query process is not completed within the active timer, the route becomes stuck-in-active (SIA).
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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