The answer is a connectivity issue causing keepalive packets to be lost, as evidenced by the repeated BGP hold timer expired notifications in the log output. When a BGP speaker sends or receives a Notification message with subcode 4/0 (Hold Timer Expired), it means that no keepalive or update messages were received within the configured hold time interval, forcing the session to reset. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to differentiate between a true session failure due to packet loss versus a configuration mismatch like mismatched hold timers—a common trap where candidates blame timer values when the real culprit is an unstable link or high CPU load. The bidirectional nature of the notifications in the output confirms that both routers are timing out, ruling out a one-sided timer misconfiguration. Memory tip: think of the hold timer as a “patience timer”—if the neighbor doesn’t hear a heartbeat (keepalive) in time, the session dies, so always check the path first.
300-410 Network Logging and Syslog Practice Question
This 300-410 practice question tests your understanding of network logging and syslog. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 on Router R4:
R4# show logging | include %BGP-3-NOTIFICATION
*Mar 1 00:01:05.123: %BGP-3-NOTIFICATION: sent to neighbor 10.0.0.2 4/0 (Hold Timer Expired) 0 bytes
*Mar 1 00:02:10.456: %BGP-3-NOTIFICATION: received from neighbor 10.0.0.2 4/0 (Hold Timer Expired) 0 bytes
*Mar 1 00:03:15.789: %BGP-3-NOTIFICATION: sent to neighbor 10.0.0.2 4/0 (Hold Timer Expired) 0 bytes
Based on this output, what is the most likely problem?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
There is a connectivity issue causing keepalive packets to be lost.
The output shows BGP notifications for hold timer expiration between R4 and neighbor 10.0.0.2. This indicates that keepalive messages are not being exchanged in time, causing the BGP session to reset repeatedly. This is typically due to a flapping link, high CPU load, or mismatched hold timers.
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 BGP neighbor has a mismatched autonomous system number.
Why it's wrong here
A mismatched AS would cause a notification with error code 2 (open message error), not hold timer expired.
✓
There is a connectivity issue causing keepalive packets to be lost.
Why this is correct
Hold timer expiration means keepalives are not received within the hold time, indicating packet loss or high delay.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The BGP update interval is too short, causing excessive updates.
Why it's wrong here
Update interval does not affect hold timer; keepalive timer is separate.
✗
The router is configured with soft-reconfiguration inbound, causing memory issues.
Why it's wrong here
Soft-reconfiguration does not cause hold timer expiration.
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.
Network Logging and Syslog — This question tests Network Logging and Syslog — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: There is a connectivity issue causing keepalive packets to be lost. — The output shows BGP notifications for hold timer expiration between R4 and neighbor 10.0.0.2. This indicates that keepalive messages are not being exchanged in time, causing the BGP session to reset repeatedly. This is typically due to a flapping link, high CPU load, or mismatched hold timers.
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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