hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures a BGP route reflector with…
An engineer configures a BGP route reflector with two clients. One client advertises a prefix to the route reflector. The route reflector reflects the prefix to the other client, but the second client does not install it in its routing table. The second client has a lower administrative distance for the same prefix from another protocol. Which is the most likely explanation?
⚠ Common exam trap
Cisco often tests the concept that route reflection only affects BGP propagation, not the route installation decision, which is governed by administrative distance or other route selection criteria like prefix length.
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 second client has a route from another protocol (e.g., OSPF) with a lower administrative distance for the same prefix, so BGP route is not installed.
A router installs only the best route for a given prefix based on administrative distance (AD) when multiple routing protocols provide routes. BGP has a default AD of 20 for eBGP and 200 for iBGP, while OSPF has an AD of 110. Since OSPF has a lower AD, the OSPF route is preferred and installed in the routing table, causing the BGP-learned prefix to be ignored even though it was successfully reflected.
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 second client has a route from another protocol (e.g., OSPF) with a lower administrative distance for the same prefix, so BGP route is not installed.
Why this is correct
Administrative distance is used to select the best route when multiple protocols provide the same prefix; a lower AD wins.
- ✗
The route reflector does not set the next-hop-self, so the next-hop is unreachable from the second client.
Why it's wrong here
While next-hop unreachability is a common issue, the scenario specifies that the second client has a route from another protocol, indicating AD is the issue.
- ✗
The route reflector is not configured as a client on the second router.
Why it's wrong here
The scenario states the route reflector is configured with two clients.
- ✗
The BGP synchronization rule is enabled and the prefix is not in the IGP.
Why it's wrong here
Synchronization is disabled by default in modern IOS versions.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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