300-410 Layer 3 Technologies Practice Question
A network technician is configuring a Cisco IOS router to authenticate EIGRP neighbors using MD5. The router is running EIGRP AS 10. Which command enables MD5 authentication for EIGRP on an interface?
⚠ Common exam trap
It's easy for candidates to confuse the command to set the authentication mode with the command to apply the key chain, or omitting the ip prefix.
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
✓
ip authentication mode eigrp 10 md5
To enable MD5 authentication for EIGRP on an interface, you must use the ip authentication mode eigrp AS-number md5 command in interface configuration mode. This sets the authentication mode to MD5. You must also configure a key chain with keys and apply it using ip authentication key-chain eigrp AS-number key-chain-name. Both sides of the link must have matching key configurations.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
ip authentication mode eigrp 10 md5
Why this is correct
This command, entered in interface configuration mode, enables MD5 authentication for EIGRP AS 10 on that interface. It specifies that EIGRP packets must be authenticated using MD5. After enabling this, you must also configure a key chain and apply it with ip authentication key-chain eigrp 10. This is the correct first step to enable MD5 authentication for EIGRP on an interface.
- ✗
authentication mode eigrp 10 md5
Why it's wrong here
This command is missing the ip prefix. The correct command in interface configuration mode is ip authentication mode eigrp 10 md5. Without the ip keyword, the command is invalid and will not enable EIGRP authentication. The router would return an error, and authentication would not be configured.
- ✗
ip eigrp authentication md5
Why it's wrong here
This command is not valid in Cisco IOS. EIGRP authentication is configured using the ip authentication mode eigrp command followed by the AS number and md5 keyword. The syntax ip eigrp authentication md5 does not exist and would be rejected by the router. Therefore, it cannot enable MD5 authentication for EIGRP.
- ✗
ip authentication key-chain eigrp 10 md5
Why it's wrong here
This command is partially correct in structure but incorrect in purpose. The actual command to apply a key chain is ip authentication key-chain eigrp 10 name-of-key-chain, without the md5 keyword. The md5 keyword is used with ip authentication mode eigrp 10 md5 to specify the authentication type. This option incorrectly combines the two commands and would not work.
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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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.