- A
The 'show ip ospf interface' command displays the authentication type and key ID configured on an interface.
Correct. The output of 'show ip ospf interface' includes fields like 'Auth' and 'Key ID' when authentication is configured.
- B
The 'debug ip ospf adj' command can show authentication mismatch errors during neighbor adjacency formation.
Correct. This debug command logs adjacency events, including authentication failures due to mismatched keys or types.
- C
OSPFv2 supports only MD5 authentication; SHA is not supported.
Why wrong: Incorrect. OSPFv2 supports both MD5 and SHA (HMAC-SHA) authentication, depending on the IOS version.
- D
Plaintext authentication is the most secure method and is recommended for production networks.
Why wrong: Incorrect. Plaintext authentication sends the password in clear text and is not secure; MD5 or SHA is recommended.
- E
The 'ip ospf authentication-key' command is used to configure SHA authentication.
Why wrong: Incorrect. The 'ip ospf authentication-key' command is used for plaintext authentication. For SHA, use 'ip ospf authentication message-digest' and 'ip ospf message-digest-key'.
300-410 OSPF Troubleshooting (v2/v3) Practice Question
This 300-410 practice question tests your understanding of ospf troubleshooting (v2/v3). 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 statements about OSPFv2 authentication troubleshooting are true? (Choose TWO.)
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 'show ip ospf interface' command displays the authentication type and key ID configured on an interface.
OSPFv2 supports MD5 and SHA authentication, and the 'show ip ospf interface' command can verify authentication configuration. The 'debug ip ospf adj' command can reveal authentication failures. Plaintext authentication is supported but deprecated, and the 'area authentication' command is used for area-level configuration.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 'show ip ospf interface' command displays the authentication type and key ID configured on an interface.
- ✓
The 'debug ip ospf adj' command can show authentication mismatch errors during neighbor adjacency formation.
Why this is correct
Correct. This debug command logs adjacency events, including authentication failures due to mismatched keys or types.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
OSPFv2 supports only MD5 authentication; SHA is not supported.
Why it's wrong here
Incorrect. OSPFv2 supports both MD5 and SHA (HMAC-SHA) authentication, depending on the IOS version.
- ✗
Plaintext authentication is the most secure method and is recommended for production networks.
Why it's wrong here
Incorrect. Plaintext authentication sends the password in clear text and is not secure; MD5 or SHA is recommended.
- ✗
The 'ip ospf authentication-key' command is used to configure SHA authentication.
Why it's wrong here
Incorrect. The 'ip ospf authentication-key' command is used for plaintext authentication. For SHA, use 'ip ospf authentication message-digest' and 'ip ospf message-digest-key'.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Trap categories for this question
Command / output trap
Incorrect. The 'ip ospf authentication-key' command is used for plaintext authentication. For SHA, use 'ip ospf authentication message-digest' and 'ip ospf message-digest-key'.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 300-410 question test?
OSPF Troubleshooting (v2/v3) — This question tests OSPF Troubleshooting (v2/v3) — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The 'show ip ospf interface' command displays the authentication type and key ID configured on an interface. — OSPFv2 supports MD5 and SHA authentication, and the 'show ip ospf interface' command can verify authentication configuration. The 'debug ip ospf adj' command can reveal authentication failures. Plaintext authentication is supported but deprecated, and the 'area authentication' command is used for area-level configuration.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
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