easyMultiple Choice
300-410 Practice Question: Runs the following command to troubleshoot a…
A network engineer runs the following command to troubleshoot a Route Redistribution issue:
R1# debug ip ospf adj
And sees the following output:
*Mar 1 00:20:11.456: OSPF: Rcv pkt from 10.1.1.2, Serial0/0/0 : Mismatch Authentication type. Input packet specified type 0, we use type 1 *Mar 1 00:20:11.457: OSPF: Rcv pkt from 10.1.1.2, Serial0/0/0 : Mismatch Authentication type. Input packet specified type 0, we use type 1
What does this output indicate?
⚠ Common exam trap
300-410 often tests the interpretation of OSPF authentication type codes, where candidates may confuse type 0 with plaintext or MD5, leading to misdiagnosis of the mismatch.
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
✓
OSPF authentication is misconfigured; the neighbor is not using authentication while this router is.
The debug output shows 'Mismatch Authentication type. Input packet specified type 0, we use type 1'. In OSPF, authentication type 0 means no authentication, while type 1 is plaintext password authentication. This indicates that the local router is configured for plaintext authentication, but the neighbor is not using authentication, causing a mismatch and preventing adjacency formation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
OSPF adjacency is forming successfully with authentication.
Why it's wrong here
The debug output reports an authentication type mismatch, so the adjacency cannot form; type 0 is null and type 1 is plaintext. It is tempting because debug ip ospf adj shows adjacency activity, but that activity here is a failure, not a successful formation.
- ✓
OSPF authentication is misconfigured; the neighbor is not using authentication while this router is.
Why this is correct
The debug output shows the neighbour's packet carrying authentication type 0 (none) while this router expects type 1 (plain text), confirming an authentication mismatch where the local interface enforces authentication the neighbour does not send.
- ✗
OSPF is redistributing routes correctly but authentication is failing.
Why it's wrong here
The mismatch occurs at the authentication stage of adjacency formation, before any database exchange, so redistribution is irrelevant to this output. It is tempting because the engineer was troubleshooting redistribution, but the debug line concerns authentication type, not redistributed routes.
- ✗
The OSPF process is using MD5 authentication and the neighbor is using plaintext.
Why it's wrong here
Type 1 is plaintext password authentication, not MD5, which is type 2. The output shows the local router using type 1 while the neighbour sends type 0, so the mismatch is plaintext versus null, not MD5 versus plaintext.
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.
Go deeper
Related to this question
Learn chapter
OSPF Neighbor Adjacency and Basics
Key term
Route Redistribution Between Protocols
Route redistribution between protocols is the process of taking routes learned from one routing protocol and injecting them into another routing protocol so that networks using different protocols can communicate.
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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.