- A
Configure a key chain with a key string on both routers.
The key chain defines the authentication key; it must be created globally with at least one key and a key string.
- B
Apply the authentication mode and key chain under the EIGRP router process.
Why wrong: EIGRP authentication is configured under the interface, not the router process.
- C
Use the 'ip authentication mode eigrp <as> md5' command on the connecting interfaces.
This interface command enables MD5 authentication for EIGRP on that interface.
- D
Set the same autonomous system number in the key chain configuration.
Why wrong: The key chain does not use the AS number; the AS is specified in the interface authentication commands.
- E
Ensure the key chain name is different on each router to prevent conflicts.
Why wrong: The key chain name must match on both routers for authentication to succeed.
Quick Answer
The answer is the 'ip authentication mode eigrp <as> md5' command on the connecting interfaces, along with a globally defined key chain that includes a key string. These two steps are required because EIGRP authentication relies on a two-part mechanism: the key chain stores the shared secret, while the interface-level command specifies the authentication algorithm—MD5 or HMAC-SHA-256—to protect routing updates. On the Cisco CCNP ENARSI 300-410 exam, this question tests your understanding that authentication is configured per interface, not under the EIGRP process itself, which is a common trap where candidates mistakenly apply it globally. Another frequent pitfall is forgetting that the key chain name must match exactly on both routers. Remember the mnemonic "Key Chain First, Interface Mode Second" to ensure you always define the key chain globally before applying the authentication mode on the interface.
300-410 EIGRP Troubleshooting Practice Question
This 300-410 practice question tests your understanding of eigrp troubleshooting. 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.
Which TWO configuration steps are required to enable EIGRP authentication between two directly connected routers? (Choose TWO.)
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
Configure a key chain with a key string on both routers.
EIGRP authentication requires a key chain with a key string and the authentication mode set to md5 (or hmac-sha-256) on the interface. The key chain must be defined globally, and then the interface configuration references it. The other options are incorrect because authentication is per-interface, not per-process, and the key chain name must match on both sides.
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.
- ✓
Configure a key chain with a key string on both routers.
Why this is correct
The key chain defines the authentication key; it must be created globally with at least one key and a key string.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Apply the authentication mode and key chain under the EIGRP router process.
Why it's wrong here
EIGRP authentication is configured under the interface, not the router process.
- ✓
Use the 'ip authentication mode eigrp <as> md5' command on the connecting interfaces.
Why this is correct
This interface command enables MD5 authentication for EIGRP on that interface.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Set the same autonomous system number in the key chain configuration.
Why it's wrong here
The key chain does not use the AS number; the AS is specified in the interface authentication commands.
- ✗
Ensure the key chain name is different on each router to prevent conflicts.
Why it's wrong here
The key chain name must match on both routers for authentication to succeed.
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.
Trap categories for this question
Command / output trap
The key chain does not use the AS number; the AS is specified in the interface authentication commands.
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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EIGRP Troubleshooting — study guide chapter
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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: Configure a key chain with a key string on both routers. — EIGRP authentication requires a key chain with a key string and the authentication mode set to md5 (or hmac-sha-256) on the interface. The key chain must be defined globally, and then the interface configuration references it. The other options are incorrect because authentication is per-interface, not per-process, and the key chain name must match on both sides.
What should I do if I get this 300-410 question wrong?
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 18, 2026
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