- A
The BGP fall-over bfd command takes precedence over the track, and since BFD is not fully operational, the session does not reset.
When both fall-over bfd and track are configured, BFD is used first. If BFD is not established, the track may not be used, causing the session to stay up.
- B
The IP SLA frequency is too low, so the track does not detect the failure quickly enough.
Why wrong: Frequency of 5 seconds is adequate; the issue is with BFD precedence.
- C
The source IP in the IP SLA must match the BGP update-source; otherwise, the track is ignored.
Why wrong: The source IP does not need to match the BGP update-source for the track to work.
- D
The track 2 is not applied to the BGP neighbor correctly; it should be under the address-family.
Why wrong: The track can be applied directly to the neighbor under the BGP router configuration.
Quick Answer
The answer is that the BGP fall-over bfd command takes precedence over the track, so the BGP session does not reset when the link fails. This happens because Cisco IOS treats BFD as the primary detection mechanism; when BGP fall-over bfd is configured, the router ignores any IP SLA tracking applied to the same neighbor, even if BFD is not fully operational. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of the interaction between IP SLA tracking and BFD—a common trap is assuming that IP SLA will still trigger a fallback when BFD is present but not working. The key insight is that BFD overrides the track, and without a working BFD session, the neighbor remains up until the hold timer expires. A useful memory tip: "BFD beats Track—if BFD is set, the track is dead."
300-410 IP SLA Practice Question
This 300-410 practice question tests your understanding of ip sla. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 configured IP SLA to track a BGP next-hop for a backup path. Router R1 has:
ip sla 2
icmp-echo 192.168.2.2 source-ip 192.168.1.1 frequency 5
ip sla schedule 2 life forever start-time now track 2 ip sla 2 reachability router bgp 65001
bgp log-neighbor-changes
neighbor 192.168.2.2 remote-as 65002 neighbor 192.168.2.2 fall-over bfd neighbor 192.168.2.2 track 2
However, when the link to 192.168.2.2 goes down, the BGP session does not reset immediately. What is the root cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"immediately / without restart"Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
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 BGP fall-over bfd command takes precedence over the track, and since BFD is not fully operational, the session does not reset.
The BGP fall-over bfd command overrides the track 2 behavior. BFD provides faster detection, but if BFD is not configured on the neighbor or if the BFD session is not established, the track might not take effect. The correct answer is that the track 2 is ignored because BGP fall-over bfd takes precedence, and BFD is not actually operational.
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 fall-over bfd command takes precedence over the track, and since BFD is not fully operational, the session does not reset.
Why this is correct
When both fall-over bfd and track are configured, BFD is used first. If BFD is not established, the track may not be used, causing the session to stay up.
Clue confirmation
The clue word "immediately / without restart" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
The IP SLA frequency is too low, so the track does not detect the failure quickly enough.
Why it's wrong here
Frequency of 5 seconds is adequate; the issue is with BFD precedence.
- ✗
The source IP in the IP SLA must match the BGP update-source; otherwise, the track is ignored.
Why it's wrong here
The source IP does not need to match the BGP update-source for the track to work.
- ✗
The track 2 is not applied to the BGP neighbor correctly; it should be under the address-family.
Why it's wrong here
The track can be applied directly to the neighbor under the BGP router configuration.
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.
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?
IP SLA — This question tests IP SLA — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The BGP fall-over bfd command takes precedence over the track, and since BFD is not fully operational, the session does not reset. — The BGP fall-over bfd command overrides the track 2 behavior. BFD provides faster detection, but if BFD is not configured on the neighbor or if the BFD session is not established, the track might not take effect. The correct answer is that the track 2 is ignored because BGP fall-over bfd takes precedence, and BFD is not actually operational.
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: "immediately / without restart". Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
2 more ways this is tested on 300-410
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An engineer configures IP SLA to track a route to a loopback address for BGP next-hop tracking. Router R1 has: ip sla 4 icmp-echo 192.168.100.1 source-ip 10.0.0.1 frequency 5 ip sla schedule 4 life forever start-time now track 4 ip sla 4 reachability router bgp 65001 neighbor 10.0.0.2 remote-as 65002 neighbor 10.0.0.2 update-source Loopback0 neighbor 10.0.0.2 ebgp-multihop 2 neighbor 10.0.0.2 fall-over bfd But the BGP session to 10.0.0.2 is flapping every 5 seconds. What is the root cause?
hard- ✓ A.The IP SLA probe is sending ICMP packets that are being rate-limited by the CoPP policy, causing the BFD session to drop.
- B.The ebgp-multihop 2 is not sufficient for the BFD session to establish.
- C.The update-source Loopback0 is not reachable from 10.0.0.2.
- D.The IP SLA schedule is set to start now, but the frequency is too high, causing the router to crash.
Why A: The IP SLA probe is sent to 192.168.100.1, but the BGP neighbor is 10.0.0.2. The track is not directly affecting the BGP session. However, the flapping is caused by the BFD session failing because the IP SLA might be interfering with the BFD packets, or more likely, the ebgp-multihop and BFD interaction. The correct answer is that the BFD session is using the same path as the IP SLA, and the IP SLA probe is causing the BFD session to reset due to packet loss or delay.
Variation 2. A network engineer configures IP SLA to track a BGP next-hop for a backup path. Router R1 has: ip sla 7 icmp-echo 192.168.3.3 source-ip 10.0.0.1 frequency 5 ip sla schedule 7 life forever start-time now track 7 ip sla 7 reachability router bgp 65001 neighbor 192.168.3.3 remote-as 65003 neighbor 192.168.3.3 fall-over bfd neighbor 192.168.3.3 track 7 But when the link to 192.168.3.3 goes down, the BGP session resets after 5 seconds, but the backup route is not used immediately. What is the root cause?
hard- ✓ A.The BGP fall-over bfd overrides the track, so the BGP session resets via BFD, but the track remains up, preventing the backup route from being installed.
- B.The IP SLA frequency is too low, so the track does not detect the failure quickly enough.
- C.The backup route has a higher administrative distance, so it is not installed until the primary route is removed, but the primary route is still present.
- D.The track 7 is not applied to the BGP neighbor correctly; it should be under the address-family.
Why A: The BGP fall-over bfd and track 7 are both configured. When the link goes down, BFD detects the failure quickly and resets the BGP session. However, the track 7 might still be up because the IP SLA probe might be successful via an alternate path, so the tracked route is not removed. The correct answer is that the track 7 is not used because BFD takes precedence, and the track does not influence the route removal.
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Last reviewed: Jun 19, 2026
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