Question 1,752 of 2,152

EIGRP Troubleshooting →hardMultiple ChoiceObjective-mapped

Troubleshooting EIGRP Active Routes and Stuck-in-Active Conditions

This 300-410 practice question tests your understanding of eigrp troubleshooting. 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.

A network engineer runs the following command on Router R1:

R1# show ip eigrp topology

EIGRP-IPv4 Topology Table for AS(100)/ID(192.168.1.1) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status

P 10.10.10.0/24, 1 successors, FD is 28160 via 10.1.1.2 (28160/28160), GigabitEthernet0/0 P 10.20.20.0/24, 1 successors, FD is 28160 via 10.2.2.2 (28160/28160), GigabitEthernet0/1 P 10.30.30.0/24, 1 successors, FD is 28160 via 10.3.3.2 (28160/28160), GigabitEthernet0/2 A 10.40.40.0/24, 0 successors, FD is Infinity via 10.4.4.2 (Infinity/Infinity), GigabitEthernet0/3

Based on this output, what is the problem?

A
The route to 10.40.40.0/24 is stuck-in-active and may cause a network instability.
A route in Active state with no successor indicates that the router is querying neighbors and has not received a reply, which can lead to SIA.
B
The route to 10.40.40.0/24 is passive and stable.
Why wrong: The code 'A' indicates Active, not Passive.
C
The route to 10.30.30.0/24 has a feasible successor.
Why wrong: The output shows only one successor for 10.30.30.0/24; no feasible successor is listed.
D
All routes are in a stable passive state.
Why wrong: The route to 10.40.40.0/24 is Active, so not all routes are passive.

Full breakdown with real-world context →

Quick Answer

The answer is that the route to 10.40.40.0/24 is stuck-in-active, which indicates a potential network instability. This is correct because the topology table shows the route in the Active state (coded as "A") with an infinite feasible distance (FD is Infinity) and zero successors, meaning the router has sent out queries for a successor but has not received all replies, leaving the route in an unresolved active state. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to troubleshoot EIGRP active state and stuck-in-active conditions, a common topic where routers fail to receive replies from neighbors due to unidirectional links, packet loss, or a neighbor going down. A common trap is confusing the "A" code with a normal query process; remember that a route stuck in Active for more than three minutes triggers the SIA condition, which can destabilize the entire EIGRP domain. Memory tip: "Active with Infinity means SIA—no successor, just a mess."

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 route to 10.40.40.0/24 is stuck-in-active and may cause a network instability.

The route to 10.40.40.0/24 is in the Active (A) state with 0 successors and an FD of Infinity, meaning the router has lost its only feasible successor and is actively querying neighbors for a new path. This is a stuck-in-active (SIA) condition because the neighbor 10.4.4.2 is not replying, causing the route to remain active indefinitely and potentially destabilizing the EIGRP domain.

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 route to 10.40.40.0/24 is stuck-in-active and may cause a network instability.
Why this is correct
A route in Active state with no successor indicates that the router is querying neighbors and has not received a reply, which can lead to SIA.
Related concept
Read the scenario before looking for a memorised answer.
✗
The route to 10.40.40.0/24 is passive and stable.
Why it's wrong here
The code 'A' indicates Active, not Passive.
✗
The route to 10.30.30.0/24 has a feasible successor.
Why it's wrong here
The output shows only one successor for 10.30.30.0/24; no feasible successor is listed.
✗
All routes are in a stable passive state.
Why it's wrong here
The route to 10.40.40.0/24 is Active, so not all routes are passive.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the distinction between the 'P' (Passive) and 'A' (Active) codes in the 'show ip eigrp topology' output, where candidates may overlook the 'A' code and assume all routes are stable, missing the SIA condition indicated by 0 successors and Infinity FD.

Trap categories for this question

Command / output trap
The output shows only one successor for 10.30.30.0/24; no feasible successor is listed.

Detailed technical explanation

How to think about this question

In EIGRP, a route enters the Active state when the last feasible successor is lost and the router must send queries to all neighbors to find an alternative path. If a neighbor fails to reply within the active timer (default 3 minutes), the route becomes stuck-in-active (SIA), and the router resets the neighbor relationship, which can cause cascading route flaps in large networks. The 'Infinity' metric (4,294,967,295) in the FD and reported distance confirms the route is unreachable and the query process is incomplete.

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.

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FAQ

Questions learners often ask

What does this 300-410 question test?

EIGRP Troubleshooting — This question tests EIGRP Troubleshooting — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The route to 10.40.40.0/24 is stuck-in-active and may cause a network instability. — The route to 10.40.40.0/24 is in the Active (A) state with 0 successors and an FD of Infinity, meaning the router has lost its only feasible successor and is actively querying neighbors for a new path. This is a stuck-in-active (SIA) condition because the neighbor 10.4.4.2 is not replying, causing the route to remain active indefinitely and potentially destabilizing the EIGRP domain.

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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Same concept, more angles

1 more ways this is tested on 300-410

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A network engineer runs the following command on Router R1: R1# show ip eigrp topology 10.50.50.0/24 EIGRP-IPv4 Topology Entry for AS(100)/ID(192.168.1.1) for 10.50.50.0/24 State: Active, Reply status: 0, Originating router: 192.168.1.1 Routing Descriptor Blocks: 10.1.1.2 (GigabitEthernet0/0), from 10.1.1.2, Send flag: 0x0 Composite metric: (4294967295/4294967295), Route is Internal Vector metric: Minimum bandwidth: 100000 Kbit Total delay: 100 microseconds Reliability: 255/255 Load: 1/255 Minimum MTU: 1500 Hop count: 1 Based on this output, what is the problem?

hard

✓ A.The route is in Active state with an infinite metric, indicating that the router has lost the route and is querying for a new path.
B.The route is passive and stable.
C.The metric of 4294967295 is normal for a summary route.
D.The hop count of 1 indicates the route is one hop away and reachable.

Why A: The route is in Active state with a composite metric of 4294967295 (the maximum 32-bit value, effectively infinite), which indicates that the router has lost the feasible successor and is actively sending queries to neighbors to find an alternative path. This is a classic sign of an EIGRP query process in progress, meaning the route is not stable or reachable.

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