hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures iBGP between two routers…
An engineer configures iBGP between two routers in the same AS. The BGP table shows the prefix, but it is not installed in the routing table. The IGP does not carry the prefix. Which is the most likely explanation?
⚠ Common exam trap
Cisco often tests the BGP synchronization rule as a legacy behavior that candidates overlook, assuming that a prefix in the BGP table always implies installation in the routing table, but synchronization can block installation even when the next-hop is reachable.
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 synchronization rule is enabled, and the prefix is not in the IGP, so BGP does not install the route.
When BGP synchronization is enabled (default in older IOS versions), BGP will not install a route learned via iBGP into the routing table unless the same prefix is also present in the IGP. Since the IGP does not carry the prefix, BGP considers the route unsynchronized and does not install it, even though it appears in the BGP table.
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 synchronization rule is enabled, and the prefix is not in the IGP, so BGP does not install the route.
Why this is correct
Synchronization requires that the prefix be reachable via IGP before BGP installs it; if not, the route remains in the BGP table but not the routing table.
- ✗
The next-hop is unreachable because of a missing static route.
Why it's wrong here
While next-hop reachability is required, the scenario specifically states the IGP does not carry the prefix, which is the synchronization issue.
- ✗
The BGP route is filtered by an inbound route-map.
Why it's wrong here
The route is in the BGP table, so it is not filtered.
- ✗
The maximum-paths limit is exceeded.
Why it's wrong here
Maximum-paths affects load balancing, not route installation.
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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.