hardMultiple ChoiceObjective-mapped
300-410 Practice Question: The default EIGRP authentication mode when…
What is the default EIGRP authentication mode when authentication is configured?
⚠ Common exam trap
Cisco often tests the distinction between 'no authentication by default' (the default state before configuration) and 'default authentication mode when authentication is configured' (which is MD5), leading candidates to incorrectly select Option D.
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
✓
MD5
When EIGRP authentication is configured, the default authentication mode is MD5. This is because EIGRP originally supported only MD5 authentication as defined in RFC 7868, and Cisco IOS/IOS-XE defaults to MD5 when the `key chain` and `authentication mode` commands are applied without specifying an alternative algorithm.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
SHA-256
Why it's wrong here
Incorrect. SHA-256 is an option but not the default; it requires the 'hmac-sha-256' keyword.
- ✓
MD5
Why this is correct
Correct. EIGRP defaults to MD5 authentication when enabled.
- ✗
Plain text
Why it's wrong here
Incorrect. EIGRP does not support plain-text authentication.
- ✗
No authentication by default
Why it's wrong here
Incorrect. When authentication is configured, the mode must be specified; MD5 is the default if not specified.
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.
Go deeper
Related to this question
Learn chapter
EIGRP Neighbor Adjacency and Basics
Key term
EIGRP Authentication
EIGRP authentication is a security feature that verifies the identity of routers exchanging routing information to prevent unauthorized or malicious updates.
Key term
OSPF and EIGRP Authentication
OSPF and EIGRP authentication is a security feature that verifies the identity of routers exchanging routing updates, ensuring only trusted devices can participate in the network.
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JA
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.