- A
The OSPF-5-ADJCHG syslog message is not generated for MTU mismatch failures because the neighbor never reaches FULL state.
Correct. MTU mismatch causes the adjacency to fail in EXSTART, and the syslog message is OSPF-4-ERRRCV instead of OSPF-5-ADJCHG.
- B
The EEM applet has a typo in the event syslog pattern; it should match 'OSPF-5-ADJCHG' with a wildcard.
Why wrong: The pattern is correctly specified; the issue is the syslog message type is different.
- C
The EEM applet requires the 'event manager run' command to be enabled globally.
Why wrong: EEM applets do not require a global 'event manager run' command; they are enabled by default.
- D
The MTU mismatch causes a routing loop that suppresses syslog generation.
Why wrong: MTU mismatch does not cause a routing loop; it prevents the adjacency from forming.
Quick Answer
The answer is that the OSPF-5-ADJCHG syslog message is not generated for MTU mismatch failures because the neighbor never reaches the FULL state. When an OSPF adjacency fails due to an MTU mismatch, the neighbor state transitions directly from EXSTART to DOWN, bypassing the FULL state entirely. The standard OSPF-5-ADJCHG syslog pattern only fires when a neighbor transitions from FULL to DOWN or vice versa, so an EEM applet monitoring that exact pattern will not trigger on an MTU mismatch. On the Cisco CCNP ENARSI 300-410 exam, this question tests your understanding of OSPF neighbor state machine behavior and the specific syslog messages generated at each stage. A common trap is assuming all adjacency failures produce the same syslog, but MTU mismatches are logged under OSPF-4-ERRRCV instead. Memory tip: “No FULL, no ADJCHG” — if the neighbor never reaches FULL, the OSPF-5-ADJCHG syslog will not fire.
300-410 Embedded Event Manager (EEM) Practice Question
This 300-410 practice question tests your understanding of embedded event manager (eem). 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.
An engineer configures an EEM applet to monitor OSPF neighbor state changes using the event syslog pattern 'OSPF-5-ADJCHG'. The applet triggers a custom syslog message. The OSPF adjacency between two routers fails due to an MTU mismatch, but the EEM applet does not trigger. Which is the most likely explanation?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 OSPF-5-ADJCHG syslog message is not generated for MTU mismatch failures because the neighbor never reaches FULL state.
When an OSPF adjacency fails due to MTU mismatch, the neighbor state transitions from EXSTART to DOWN without generating the standard OSPF-5-ADJCHG syslog message. The adjacency never reaches FULL, so the state change from EXSTART to DOWN is logged as a different syslog pattern (OSPF-4-ERRRCV or OSPF-5-ADJCHG may not fire). EEM applets that rely on the exact pattern 'OSPF-5-ADJCHG' will not trigger because that message is only generated when the neighbor state changes from FULL to DOWN or vice versa.
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 OSPF-5-ADJCHG syslog message is not generated for MTU mismatch failures because the neighbor never reaches FULL state.
- ✗
The EEM applet has a typo in the event syslog pattern; it should match 'OSPF-5-ADJCHG' with a wildcard.
Why it's wrong here
The pattern is correctly specified; the issue is the syslog message type is different.
- ✗
The EEM applet requires the 'event manager run' command to be enabled globally.
Why it's wrong here
EEM applets do not require a global 'event manager run' command; they are enabled by default.
- ✗
The MTU mismatch causes a routing loop that suppresses syslog generation.
Why it's wrong here
MTU mismatch does not cause a routing loop; it prevents the adjacency from forming.
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
EEM applets do not require a global 'event manager run' command; they are enabled by default.
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?
Embedded Event Manager (EEM) — This question tests Embedded Event Manager (EEM) — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The OSPF-5-ADJCHG syslog message is not generated for MTU mismatch failures because the neighbor never reaches FULL state. — When an OSPF adjacency fails due to MTU mismatch, the neighbor state transitions from EXSTART to DOWN without generating the standard OSPF-5-ADJCHG syslog message. The adjacency never reaches FULL, so the state change from EXSTART to DOWN is logged as a different syslog pattern (OSPF-4-ERRRCV or OSPF-5-ADJCHG may not fire). EEM applets that rely on the exact pattern 'OSPF-5-ADJCHG' will not trigger because that message is only generated when the neighbor state changes from FULL to DOWN or vice versa.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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