- A
High packet loss on the link between R2 and R3 causes EIGRP queries or replies to be dropped, leading to SIA.
EIGRP relies on reliable transport; packet loss can cause queries to remain unanswered, triggering SIA after the active timer expires.
- B
R3 has a route summarization that causes the query to be sent to the Null0 interface.
Why wrong: Summarization could cause issues, but the SIA is due to lost packets, not summarization.
- C
The EIGRP active timer is set too low on R1, causing premature SIA.
Why wrong: The active timer default is 3 minutes; packet loss is a more likely cause than timer misconfiguration.
- D
R2 has a distribute-list that filters the prefix, preventing the reply from being sent.
Why wrong: If a distribute-list blocked the prefix, the route would not be in the topology table; SIA occurs when a query is sent but no reply is received.
EIGRP SIA: Root Cause Analysis with Packet Loss
This 300-410 practice question tests your understanding of device management. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 EIGRP network with routers R1, R2, and R3 is experiencing frequent Stuck-in-Active (SIA) events for the prefix 172.16.1.0/24. R1 is the successor, R2 is the feasible successor. R3 is a query originator. 'show ip eigrp topology 172.16.1.0/24' on R1 shows the route in active state. 'show ip eigrp interfaces' on R2 shows the link to R3 is up but with high packet loss. What is the root cause?
Quick Answer
The answer is high packet loss on the link between R2 and R3, which causes EIGRP queries or replies to be dropped, leading to a Stuck-in-Active (SIA) condition. This is correct because EIGRP relies on reliable delivery of queries and replies during the Diffusing Update Algorithm (DUAL) process; when a query originator like R3 sends a query to its feasible successor R2, and the reply is lost due to packet loss, R1 never receives the reply within the active timer, forcing the route to remain in the active state. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to correlate SIA events with Layer 2 or Layer 3 reliability issues rather than misconfigurations—a common trap is to blame the query originator or adjust timers first, but the root cause is the unreliable link. Memory tip: “SIA means ‘Some Interface is Absent’—check for packet loss on the query path, not just the successor link.”
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
High packet loss on the link between R2 and R3 causes EIGRP queries or replies to be dropped, leading to SIA.
The correct answer is A because the high packet loss on the link between R2 and R3 causes EIGRP queries or replies to be dropped. When R3 originates a query for the prefix 172.16.1.0/24, R1 (the successor) transitions the route to active state and sends queries to all neighbors, including R2. R2, as the feasible successor, must reply, but if the link to R3 has high packet loss, the query from R2 to R3 or the reply from R3 back to R2 may be lost, preventing R2 from sending its reply to R1 within the active timer, leading to a Stuck-in-Active (SIA) event.
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.
- ✓
High packet loss on the link between R2 and R3 causes EIGRP queries or replies to be dropped, leading to SIA.
Why this is correct
EIGRP relies on reliable transport; packet loss can cause queries to remain unanswered, triggering SIA after the active timer expires.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
R3 has a route summarization that causes the query to be sent to the Null0 interface.
Why it's wrong here
Summarization could cause issues, but the SIA is due to lost packets, not summarization.
- ✗
The EIGRP active timer is set too low on R1, causing premature SIA.
Why it's wrong here
The active timer default is 3 minutes; packet loss is a more likely cause than timer misconfiguration.
- ✗
R2 has a distribute-list that filters the prefix, preventing the reply from being sent.
Why it's wrong here
If a distribute-list blocked the prefix, the route would not be in the topology table; SIA occurs when a query is sent but no reply is received.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that SIA is always caused by a slow or congested link directly between the query originator and the successor, but here the trap is that the packet loss is on the link between R2 and R3, which indirectly prevents R2 from replying to R1, causing SIA.
Detailed technical explanation
How to think about this question
EIGRP uses Reliable Transport Protocol (RTP) for query and reply messages, which requires acknowledgment; if packets are lost due to high link loss, RTP retransmits up to 16 times (by default) before declaring the neighbor dead, but the active timer (default 3 minutes) may expire before retransmissions succeed, causing SIA. In real-world scenarios, high packet loss on a single link can cause SIA events even if other links are healthy, as the query propagation depends on all neighbors replying within the active timer.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Device Management — study guide chapter
Learn the concepts, then practise the questions
- →
Device Management practice questions
Targeted practice on this topic area only
- →
All 300-410 questions
2,152 questions across all exam domains
- →
Cisco CCNP ENARSI 300-410 study guide
Full concept coverage aligned to exam objectives
- →
300-410 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 300-410 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Layer 3 Technologies practice questions
Practise 300-410 questions linked to Layer 3 Technologies.
EIGRP Troubleshooting practice questions
Practise 300-410 questions linked to EIGRP Troubleshooting.
OSPF Troubleshooting (v2/v3) practice questions
Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).
BGP Troubleshooting practice questions
Practise 300-410 questions linked to BGP Troubleshooting.
Route Redistribution practice questions
Practise 300-410 questions linked to Route Redistribution.
Policy-Based Routing (PBR) practice questions
Practise 300-410 questions linked to Policy-Based Routing (PBR).
VRF-Lite practice questions
Practise 300-410 questions linked to VRF-Lite.
Route Maps and Route Filtering practice questions
Practise 300-410 questions linked to Route Maps and Route Filtering.
Administrative Distance practice questions
Practise 300-410 questions linked to Administrative Distance.
Route Summarization practice questions
Practise 300-410 questions linked to Route Summarization.
Bidirectional Forwarding Detection (BFD) practice questions
Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).
VPN Technologies practice questions
Practise 300-410 questions linked to VPN Technologies.
Practice this exam
Start a free 300-410 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 300-410 question test?
Device Management — This question tests Device Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: High packet loss on the link between R2 and R3 causes EIGRP queries or replies to be dropped, leading to SIA. — The correct answer is A because the high packet loss on the link between R2 and R3 causes EIGRP queries or replies to be dropped. When R3 originates a query for the prefix 172.16.1.0/24, R1 (the successor) transitions the route to active state and sends queries to all neighbors, including R2. R2, as the feasible successor, must reply, but if the link to R3 has high packet loss, the query from R2 to R3 or the reply from R3 back to R2 may be lost, preventing R2 from sending its reply to R1 within the active timer, leading to a Stuck-in-Active (SIA) event.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More 300-410 practice questions
- Drag and drop the steps to negotiate an IKEv2 IPsec site-to-site tunnel into the correct order, from first to last.
- Drag and drop the steps to troubleshoot an IPsec site-to-site VPN adjacency failure into the correct order, from first t…
- Drag and drop the steps to verify and validate the operational state of an IPsec site-to-site VPN into the correct order…
- Consider the following configuration snippet: ip cef ! interface GigabitEthernet0/0 ip address 10.0.0.1 255.255.255.25…
- A router is configured with 'logging host 10.1.1.100' and 'logging trap informational'. The engineer notices that syslog…
- Drag and drop the steps to configure a GRE tunnel for IPv6 over IPv4 into the correct order, from first to last.
Last reviewed: Jul 4, 2026
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.