- 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.
EIGRP Authentication Configuration
This 300-410 practice question tests your understanding of eigrp troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.)
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.
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.
Option A is correct because EIGRP authentication requires a key chain to be configured on both routers, which defines the key string (the actual password) used for authentication. Without a matching key string in the key chain, the authentication process will fail, as the routers cannot validate each other's EIGRP packets.
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
Cisco often tests the misconception that EIGRP authentication is configured under the router process (like OSPF) rather than on the interface, leading candidates to incorrectly select Option B.
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
EIGRP authentication uses MD5 or SHA-256 hashing to ensure that only trusted routers can exchange routing updates. The key chain allows for key rotation with time-based lifetimes, which is critical in large networks to avoid service disruption during key changes. The authentication is applied per interface, not globally, because different interfaces may require different keys or authentication modes.
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 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.
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.
- →
EIGRP Troubleshooting — study guide chapter
Learn the concepts, then practise the questions
- →
EIGRP Troubleshooting 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?
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. — Option A is correct because EIGRP authentication requires a key chain to be configured on both routers, which defines the key string (the actual password) used for authentication. Without a matching key string in the key chain, the authentication process will fail, as the routers cannot validate each other's EIGRP packets.
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.