Question 124 of 2,152

IP SLA →hardMultiple ChoiceObjective-mapped

IP SLA Responder Control Port Mismatch: Troubleshooting Timeouts

This 300-410 practice question tests your understanding of ip sla. 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.

A network engineer configures IP SLA with a UDP echo operation to monitor a remote server. The IP SLA responder is configured on the remote router. The engineer notices that the operation shows 'Timeout' intermittently, but standard UDP connectivity tests from the router to the server succeed. The engineer checks the IP SLA responder configuration and finds that the control port is set to a non-default value. 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.

A
The IP SLA responder is not configured to respond to UDP echo requests from the initiator.
Why wrong: The responder is configured, but the control port mismatch prevents proper setup.
B
The IP SLA initiator must be configured with the 'control' keyword to match the non-default control port on the responder.
The control port mismatch causes the initiator to fail to establish the operation, leading to timeouts.
C
The UDP echo operation uses a different protocol than standard UDP, causing packet drops.
Why wrong: UDP echo uses standard UDP; the issue is control port.
D
The IP SLA operation has a threshold that is too low, causing the operation to time out.
Why wrong: Threshold does not cause timeouts; timeout does.

Full breakdown with real-world context →

Quick Answer

The answer is that the IP SLA initiator must be configured with the control keyword to match the non-default control port on the responder. This is because IP SLA UDP echo operations rely on a dedicated control channel, using UDP port 1967 by default, to negotiate test parameters and synchronize the probe. When the responder’s control port is changed to a non-default value, the initiator still attempts to communicate on port 1967, causing the responder to ignore the setup messages—leading to intermittent timeouts even though standard UDP connectivity succeeds. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of the IP SLA responder architecture and the critical distinction between the data-plane echo port and the control-plane negotiation port. A common trap is assuming that a successful ping or UDP test to the target IP means the IP SLA operation should work, but the timeout actually stems from a control port mismatch, not a reachability issue. Remember the memory tip: “Control the control port” — if the responder changes its control port, the initiator must explicitly match it with the control keyword.

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 IP SLA initiator must be configured with the 'control' keyword to match the non-default control port on the responder.

IP SLA UDP echo operations require the IP SLA responder to be configured with the correct control port. If the responder uses a non-default control port, the initiator must be configured to use that port using the 'control' keyword under the IP SLA operation. Without this, the initiator uses the default control port (1967), causing communication failures and intermittent timeouts.

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 IP SLA responder is not configured to respond to UDP echo requests from the initiator.
Why it's wrong here
The responder is configured, but the control port mismatch prevents proper setup.
✓
The IP SLA initiator must be configured with the 'control' keyword to match the non-default control port on the responder.
Why this is correct
The control port mismatch causes the initiator to fail to establish the operation, leading to timeouts.
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.
✗
The UDP echo operation uses a different protocol than standard UDP, causing packet drops.
Why it's wrong here
UDP echo uses standard UDP; the issue is control port.
✗
The IP SLA operation has a threshold that is too low, causing the operation to time out.
Why it's wrong here
Threshold does not cause timeouts; timeout does.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.

Detailed technical explanation

How to think about this question

This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.

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.
Use explanations to understand the rule behind the answer.

TExam Day Tips

Underline the problem statement mentally.
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 practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.

What to study next

Got this wrong? Here's your next step.

Identify which 300-410 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

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FAQ

Questions learners often ask

What does this 300-410 question test?

IP SLA — This question tests IP SLA — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The IP SLA initiator must be configured with the 'control' keyword to match the non-default control port on the responder. — IP SLA UDP echo operations require the IP SLA responder to be configured with the correct control port. If the responder uses a non-default control port, the initiator must be configured to use that port using the 'control' keyword under the IP SLA operation. Without this, the initiator uses the default control port (1967), causing communication failures and intermittent timeouts.

What should I do if I get this 300-410 question wrong?

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.

About these practice questions

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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. An engineer configures IP SLA with a UDP jitter operation to monitor VoIP quality between two routers. The operation shows 'OverThreshold' in the show ip sla statistics output, but the engineer notices that the IP SLA responder on the remote router is configured with a control port that does not match the default. Which is the most likely explanation?

hard

A.The IP SLA responder control port mismatch causes the operation to use a different port, but the jitter calculation is unaffected.
✓ B.The IP SLA initiator must be configured with the 'control' keyword to specify the non-default control port on the responder.
C.The IP SLA responder automatically adjusts its control port to match the initiator's request.
D.The UDP jitter operation does not use the control port; it only uses the destination port for jitter probes.

Why B: IP SLA UDP jitter operations require the IP SLA responder to be configured with the correct control port; if the responder uses a non-default control port, the IP SLA initiator must be configured to use that port via the 'control' keyword under the IP SLA operation, otherwise the operation fails or produces incorrect results.

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