The answer is that OSPF authentication is misconfigured, specifically the neighbor is not using authentication while this router expects type 1 (plaintext authentication). This is correct because the debug ip ospf adj output clearly shows a mismatch where the received packet specifies authentication type 0 (none), but the local router is configured for type 1, preventing the OSPF adjacency from forming. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to troubleshoot OSPF adjacency authentication mismatch impacting route redistribution, as a failed adjacency means OSPF cannot exchange routes, directly breaking redistribution into or from OSPF. A common trap is confusing authentication type 0 (no auth) with type 2 (MD5); remember that type 1 is plaintext and type 2 is cryptographic. Memory tip: “Type 1 is plain, type 2 is pain (to configure), type 0 is no gain (no adjacency).”
300-410 Route Redistribution Practice Question
This 300-410 practice question tests your understanding of route redistribution. 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.
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
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 ip ospf adj output shows authentication type mismatch. The router expects type 1 (plaintext authentication) but the received packet has type 0 (no authentication). This prevents the OSPF adjacency from forming, which would affect route redistribution if OSPF is not learning routes.
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.
✗
OSPF adjacency is forming successfully with authentication.
Why it's wrong here
The mismatch prevents adjacency from forming.
✓
OSPF authentication is misconfigured; the neighbor is not using authentication while this router is.
Why this is correct
The router expects authentication type 1, but the neighbor sends type 0, indicating a configuration mismatch.
OSPF is redistributing routes correctly but authentication is failing.
Why it's wrong here
Redistribution is not relevant here; the adjacency itself is failing.
✗
The OSPF process is using MD5 authentication and the neighbor is using plaintext.
Why it's wrong here
Type 1 is plaintext; MD5 is type 2. The mismatch is between type 0 and type 1.
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.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
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.
Route Redistribution — This question tests Route Redistribution — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: OSPF authentication is misconfigured; the neighbor is not using authentication while this router is. — The debug ip ospf adj output shows authentication type mismatch. The router expects type 1 (plaintext authentication) but the received packet has type 0 (no authentication). This prevents the OSPF adjacency from forming, which would affect route redistribution if OSPF is not learning routes.
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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