The answer is that BGP is using BFD with the state UP, enabling sub-second failure detection for this prefix. This is correct because the output of the show bgp ipv4 unicast command explicitly includes the lines “BFD enabled, BFD state: UP,” confirming that the Bidirectional Forwarding Detection protocol is actively monitoring the BGP session to the neighbor at 10.1.1.2. BFD provides rapid link failure detection far faster than BGP’s default keepalive and hold timers, which is critical for fast convergence in modern networks. On the Cisco CCNP ENARSI 300-410 exam, bfd verification bgp questions often test your ability to interpret this exact command output, as the “BFD state: UP” line is the key indicator that fast failure detection is operational. A common trap is assuming BFD is working just because it is configured; you must verify the state is UP, not DOWN or ADMIN DOWN. Memory tip: “BFD UP means fast failover—if it’s DOWN, BGP won’t blink.”
300-410 Bidirectional Forwarding Detection (BFD) Practice Question
This 300-410 practice question tests your understanding of bidirectional forwarding detection (bfd). 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.
A network engineer runs the following command to troubleshoot BFD with BGP:
R1# show bgp ipv4 unicast 10.3.3.0/24
BGP routing table entry for 10.3.3.0/24, version 2
Paths: (1 available, best #1, table default)
Advertised to update-groups:
1
Refresh Epoch 1
Local
10.1.1.2 from 10.1.1.2 (2.2.2.2)
Origin IGP, metric 0, localpref 100, valid, external, best
rx pathid: 0, tx pathid: 0x0
BFD enabled, BFD state: UP
What does this output indicate?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
BGP is using BFD with state UP, enabling sub-second failure detection for this prefix.
The output shows that BFD is enabled for the BGP session and the BFD state is UP, indicating fast failure detection for the BGP neighbor.
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.
✓
BGP is using BFD with state UP, enabling sub-second failure detection for this prefix.
Why this is correct
BFD is enabled and UP, allowing BGP to detect failures faster than BGP keepalive/hold timers.
Clue confirmation
The clue word "best" in the question point toward this answer.
This is an IPv4 unicast prefix; BFD is enabled for IPv4.
Common exam traps
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.
Trap categories for this question
Command / output trap
The output shows 'BFD enabled'.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
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 300-410 OSPF questions on adjacency and route selection.
Bidirectional Forwarding Detection (BFD) — This question tests Bidirectional Forwarding Detection (BFD) — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: BGP is using BFD with state UP, enabling sub-second failure detection for this prefix. — The output shows that BFD is enabled for the BGP session and the BFD state is UP, indicating fast failure detection for the BGP neighbor.
What should I do if I get this 300-410 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 300-410 OSPF questions on adjacency and route selection.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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