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 engineer notices that routes learned from one iBGP neighbor are not being advertised to another iBGP neighbor, even though the next-hop is reachable. The engineer verifies that the BGP session is established and that the routes are present in the BGP table. Which is the most likely explanation?
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
✓
iBGP split-horizon rule prevents advertising iBGP-learned routes to other iBGP neighbors
By default, iBGP routers do not advertise routes learned from one iBGP neighbor to another iBGP neighbor because of the split-horizon rule. This is a fundamental behavior to prevent routing loops, but it often catches engineers who expect iBGP to behave like eBGP. To overcome this, a route reflector or confederation must be used.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
iBGP split-horizon rule prevents advertising iBGP-learned routes to other iBGP neighbors
Why this is correct
Correct. iBGP does not advertise routes learned from one iBGP neighbor to another iBGP neighbor by default.
- ✗
The next-hop-self command is required for iBGP
Why it's wrong here
Next-hop-self is typically used for eBGP or when the next-hop is not reachable via IGP, but it is not the cause of this issue.
- ✗
The BGP synchronization rule is enabled
Why it's wrong here
Synchronization would prevent routes from being used if not present in IGP, but it does not prevent advertisement between iBGP neighbors.
- ✗
The routes are not valid because the next-hop is not reachable
Why it's wrong here
The engineer stated the next-hop is reachable, so this is not the issue.
Go deeper
Related to this question
Learn chapter
OSPF Neighbor Adjacency and Basics
Key term
BGP Route Reflector
A BGP Route Reflector is a networking device that reduces the number of BGP peer connections needed in a large network by allowing routers to share routing information without needing to connect to every other router directly.
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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.