hardMultiple Choice
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
With BGP synchronization enabled, a route learned via iBGP is not installed in the routing table unless the same prefix exists in the IGP. Since the IGP does not carry it, the route stays in the BGP table only, matching the stem exactly.
- ✗
The next-hop is unreachable because of a missing static route.
Why it's wrong here
iBGP does not rewrite the next hop, so it must be reachable via the IGP or a static route; a missing static route is a plausible cause, but the stem already states the IGP does not carry the prefix, making next-hop reachability the actual issue rather than the specific remedy.
- ✗
The BGP route is filtered by an inbound route-map.
Why it's wrong here
An inbound route-map denying the prefix would stop it entering the BGP table entirely, so the prefix would not appear at all. Its presence in the table with no RIB entry points to the next-hop being unreachable, since the IGP does not carry it. Route-maps are for filtering or manipulating attributes, not next-hop resolution.
- ✗
The maximum-paths limit is exceeded.
Why it's wrong here
iBGP requires the next-hop to be reachable via the IGP or a static route; without it, the route is marked inaccessible and never installed, regardless of path count. Maximum-paths only governs ECMP load-sharing across multiple equal-cost entries already eligible for the RIB.
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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.