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300-410 Practice Question: An enterprise uses IP SLA to track a route to a…
An enterprise uses IP SLA to track a route to a remote site via two ISPs. Router R1 has:
ip sla 3
icmp-echo 8.8.8.8 source-ip 10.0.0.1 frequency 10
ip sla schedule 3 life forever start-time now track 3 ip sla 3 reachability ip route 10.10.10.0 255.255.255.0 10.0.0.2 track 3 ip route 10.10.10.0 255.255.255.0 10.0.1.2 10
When the primary ISP fails, the backup route is used, but traffic to 10.10.10.0/24 is intermittently lost. Show output on R1:
show ip route 10.10.10.0 Routing entry for 10.10.10.0/24 Known via "static", distance 1, metric 0 Last update from 10.0.0.2 on GigabitEthernet0/0
* 10.0.1.2, via GigabitEthernet0/1
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 IP SLA probe to 8.8.8.8 is successful via the backup path, so the track remains up, but the primary next-hop 10.0.0.2 is down, causing traffic to be sent to a dead next-hop.
The tracked route is still present in the routing table even though the track is down. This happens because the track is only removed if the track state is 'down', but the show output shows the route is still there. The likely cause is that the track is not properly associated with the route, or the route has a higher administrative distance that is not being overridden. However, the correct answer is that the track 3 is configured with 'reachability' but the IP SLA probe may be successful due to a different path, so the track remains up, but the primary next-hop is actually unreachable, causing packet loss.
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 IP SLA probe to 8.8.8.8 is successful via the backup path, so the track remains up, but the primary next-hop 10.0.0.2 is down, causing traffic to be sent to a dead next-hop.
Why this is correct
The track monitors reachability to 8.8.8.8, not the next-hop. If the backup path can reach 8.8.8.8, the track stays up, and the primary route remains installed even though the next-hop is unreachable.
- ✗
The backup route has a higher administrative distance, so it is not installed until the primary route is removed, but the track is not removing the primary route.
Why it's wrong here
The backup route has distance 10, but the primary route is still installed because the track is up.
- ✗
The IP SLA frequency is too low, causing a delay in track state change.
Why it's wrong here
Frequency is not the issue; the probe is succeeding via the backup path.
- ✗
The track should be configured with 'ip sla 3 state' instead of 'reachability' to monitor the next-hop.
Why it's wrong here
Reachability is correct for tracking reachability to a target; the issue is the target is not the next-hop.
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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.