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350-401 Practice Question: Router R5 has the following OSPF configuration:…
Router R5 has the following OSPF configuration: router ospf 1
router-id 5.5.5.5
network 10.0.0.0 0.255.255.255 area 0 area 0 authentication message-digest
!
interface GigabitEthernet0/0 ip address 10.1.1.5 255.255.255.0 ip ospf message-digest-key 1 md5 cisco123
What is missing from this OSPF authentication configuration?
⚠ Common exam trap
Many candidates assume configuring the area authentication and the key is sufficient, overlooking the mandatory interface-level `ip ospf authentication message-digest` command that activates authentication on the specific 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
✓
The interface needs the 'ip ospf authentication message-digest' command.
OSPF authentication configuration requires two components: an area-level authentication type (configured via `area 0 authentication message-digest`) and an interface-level authentication mode (configured via `ip ospf authentication message-digest`). The interface command tells the OSPF process to actually use the key defined with `ip ospf message-digest-key`. Without it, the interface defaults to no authentication, even though the area is configured for authentication.
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 configuration is complete and correct.
Why it's wrong here
The interface is missing the 'ip ospf authentication message-digest' command to enable authentication.
- ✓
The interface needs the 'ip ospf authentication message-digest' command.
Why this is correct
This command activates MD5 authentication on the interface, required for the area authentication to take effect.
- ✗
The 'area 0 authentication' command should be 'area 0 authentication md5'.
Why it's wrong here
The correct syntax is 'area 0 authentication message-digest' for MD5 authentication.
- ✗
The 'network' command should include the area authentication keyword.
Why it's wrong here
The network command does not include authentication parameters; it is configured under the interface.
Visual reference
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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 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 350-401 exam.