hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Configured IP SLA to track a BGP next-hop for a…
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?
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.
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.
- ✗
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.
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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 B: The BGP session flaps every 5 seconds because BFD is enabled with 'fall-over bfd', but ebgp-multihop 2 alone is not sufficient for BFD to establish over a multihop eBGP session. BFD requires explicit multihop configuration under the BGP process or interface, such as the 'bfd interval' command with the 'multihop' keyword. Without this, BFD fails to establish, causing BGP to detect a neighbor failure and flap the session. The 5-second interval matches the default BFD failure detection timing, not the IP SLA frequency.
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.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.