easyMultiple Choice
300-410 Practice Question: Is troubleshooting a BGP route advertisement issue
A network engineer is troubleshooting a BGP route advertisement issue. Router R1 (AS 65001) has an eBGP session with R2 (AS 65002). R1 is advertising the prefix 192.168.1.0/24 to R2. On R2, the route appears in the BGP table but is not installed in the routing table. The output of 'show ip bgp 192.168.1.0/24' on R2 shows the route as valid, best, but with the 'r' flag (RIB-failure). The routing table on R2 shows a static route for 192.168.1.0/24 with administrative distance 1. What is the most likely 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 route is not installed because a static route with a lower administrative distance exists for the same prefix.
RIB-failure occurs when BGP tries to install a route but a route with a lower administrative distance already exists. Here, the static route (AD 1) is preferred over the eBGP route (AD 20).
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 route is not installed because a static route with a lower administrative distance exists for the same prefix.
Why this is correct
The 'r' flag indicates RIB-failure: BGP selected the route as valid and best, but installation failed because a static route with administrative distance 1 is preferred over eBGP's distance of 20 for the same prefix.
- ✗
The BGP route is not installed because the next-hop is unreachable.
Why it's wrong here
A RIB-failure with the route marked valid and best indicates the next-hop resolved fine; an unreachable next-hop would instead show the route as invalid. The static route with administrative distance 1 simply outranks the eBGP route during best-path selection into the RIB.
- ✗
The BGP route is not installed because BGP synchronization is enabled.
Why it's wrong here
Synchronisation only blocks iBGP routes until the IGP carries them; here the peer is eBGP and the route already shows valid and best, so synchronisation is not suppressing it. It would be the answer when an iBGP-learned prefix is withheld pending IGP reachability.
- ✗
The BGP route is not installed because the prefix length is too long.
Why it's wrong here
Prefix length is irrelevant: the route is already marked valid and best, so it passed BGP's own checks. RIB-failure arises only when a competing source wins the administrative-distance comparison — here the static route with AD 1. Length limits matter for filtering, not RIB 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.