The answer is an incorrect BGP neighbor statement on the route reflector or client. When a BGP session remains in the Active state, it indicates that the router is actively trying to initiate a TCP connection but failing to establish it, which almost always points to a misconfiguration in the neighbor statement—such as a wrong IP address, incorrect AS number, or a missing neighbor command on one side. In the context of BGP route reflector active state troubleshooting, this is a fundamental concept tested on the Cisco SPCOR 350-501 exam, where you must distinguish between session establishment issues and route propagation problems. A common trap is confusing the Active state with route filtering or next-hop issues, but those affect route advertisement, not the TCP session itself. Remember the memory tip: Active means “attempting to connect”—check your neighbor statements first, not your route policies.
350-501 Networking Practice Question
This 350-501 practice question tests your understanding of networking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An engineer is troubleshooting a BGP route reflector setup. Clients are not receiving all routes. The 'show bgp neighbors' output shows a state of 'Active'. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Incorrect BGP neighbor statement on the route reflector or client
Option B is correct because the BGP session is in Active state, meaning the router is trying to connect but not succeeding, often due to a missing or incorrect neighbor configuration. Option A (Route reflectors do not peer with clients) is false; Option C (AS_PATH loop detection) would not prevent session establishment; Option D (next-hop reachability) does not affect BGP session state.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 route reflector does not have a full mesh with clients
Why it's wrong here
Route reflectors do not need full mesh with clients.
✗
The route reflector is detecting an AS_PATH loop
Why it's wrong here
Loop detection would not cause Active state.
✗
Next-hop reachability issue
Why it's wrong here
Next-hop reachability is for route installation, not session state.
✓
Incorrect BGP neighbor statement on the route reflector or client
Why this is correct
Active state indicates TCP session failure, often due to misconfiguration.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 350-501 OSPF questions on adjacency and route selection.
Networking — This question tests Networking — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Incorrect BGP neighbor statement on the route reflector or client — Option B is correct because the BGP session is in Active state, meaning the router is trying to connect but not succeeding, often due to a missing or incorrect neighbor configuration. Option A (Route reflectors do not peer with clients) is false; Option C (AS_PATH loop detection) would not prevent session establishment; Option D (next-hop reachability) does not affect BGP session state.
What should I do if I get this 350-501 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 350-501 OSPF questions on adjacency and route selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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