The answer is that the EEM applet itself is the root cause of the BGP prefix limit flapping, because it clears the BGP session upon detecting the "%BGP-3-PREFIX_LIMIT" syslog message, which resets the prefix counter but does nothing to stop the neighbor from re-advertising the same excessive prefixes. This creates a destructive cycle: the prefix limit is hit, the session is cleared, the neighbor re-establishes and re-sends the same prefixes, the limit is hit again, and the session flaps repeatedly. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding that EEM actions must address the underlying cause—such as increasing the prefix limit or applying a prefix-list filter—rather than just resetting the session. A common trap is assuming that clearing the session permanently resolves the issue, but it only provides a temporary reset. Memory tip: “Clear the cause, not the symptom”—if you clear the session, you’ll just flap again.
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.
A network engineer configures EEM to monitor BGP prefix limits on R1. R1 has: event manager applet BGP-PREFIX event syslog pattern "%BGP-3-PREFIX_LIMIT" action 1.0 cli command "enable" action 2.0 cli command "clear ip bgp 10.1.1.2" action 3.0 syslog msg "Cleared BGP session". Router R2 shows: BGP session with R1 is flapping, and logs show repeated prefix limit warnings. What is the root cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The EEM applet clears the BGP session, which resets the prefix count but does not prevent the neighbor from re-sending the same prefixes.
The EEM applet clears the BGP session when a prefix limit is reached, but this does not solve the underlying issue. The prefix limit is exceeded because the neighbor is sending too many prefixes; clearing the session only temporarily resets the count, leading to a cycle. The correct fix is to increase the prefix limit or filter prefixes.
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 EEM applet clears the BGP session, which resets the prefix count but does not prevent the neighbor from re-sending the same prefixes.
Why this is correct
Clearing the session only provides temporary relief; the prefix limit is hit again after re-establishment.
The clear command should be 'clear ip bgp *' to reset all sessions.
Why it's wrong here
Clearing all sessions would cause more disruption; the issue is the underlying prefix limit.
✗
The BGP session is flapping due to a keepalive timer mismatch.
Why it's wrong here
No keepalive timer configuration is shown; the flapping is caused by the EEM clear command.
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
No keepalive timer configuration is shown; the flapping is caused by the EEM clear command.
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.
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 EEM applet clears the BGP session, which resets the prefix count but does not prevent the neighbor from re-sending the same prefixes. — The EEM applet clears the BGP session when a prefix limit is reached, but this does not solve the underlying issue. The prefix limit is exceeded because the neighbor is sending too many prefixes; clearing the session only temporarily resets the count, leading to a cycle. The correct fix is to increase the prefix limit or filter prefixes.
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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