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300-410 Practice Question: Runs the following command to troubleshoot an…
A network engineer runs the following command to troubleshoot an EIGRP issue:
R1# debug eigrp packets hello *Mar 1 00:05:23.123: EIGRP: received packet with MD5 authentication, key id = 1 *Mar 1 00:05:23.123: EIGRP: int GigabitEthernet0/0, src 10.1.1.2 dst 224.0.0.10, seq 0, ttl 1, opcode = 1 (Hello) *Mar 1 00:05:23.123: EIGRP: authentication failed for packet from 10.1.1.2, key id = 1, integrity check failed
What does this output indicate?
⚠ Common exam trap
Cisco often tests the distinction between authentication failure due to a mismatch (which prevents neighbor formation) versus intermittent packet loss or misconfiguration of the authentication mode (e.g., confusing MD5 with plain-text).
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 MD5 key ID or key string does not match between R1 and 10.1.1.2, preventing neighbor formation.
The debug output shows an EIGRP packet with MD5 authentication was received from 10.1.1.2, but the integrity check failed. This indicates that the MD5 key ID or key string configured on R1 does not match the one on the neighbor, which prevents the neighbor relationship from forming. The 'integrity check failed' message is a definitive sign of an authentication mismatch, not an intermittent issue.
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 EIGRP neighbor relationship is up, but authentication is failing intermittently.
Why it's wrong here
The neighbor relationship cannot form because authentication fails on every packet.
- ✓
The MD5 key ID or key string does not match between R1 and 10.1.1.2, preventing neighbor formation.
Why this is correct
The integrity check failure indicates a key mismatch, which blocks neighbor adjacency.
- ✗
EIGRP is using plain-text authentication and the key is incorrect.
Why it's wrong here
The debug explicitly states MD5 authentication, not plain-text.
- ✗
The neighbor 10.1.1.2 is not configured for EIGRP authentication.
Why it's wrong here
The packet includes authentication, so the neighbor is configured, but the keys do not match.
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.