This LFCS 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.
A server has two NICs bonded in mode 1 (active-backup). If the active NIC fails, what occurs?
Both NICs continue to pass traffic simultaneously
Why wrong: Only one NIC is active at a time in mode 1.
Traffic automatically switches to the backup NIC with minimal interruption
Active-backup provides automatic failover.
The bond interface goes down until an administrator intervenes
Why wrong: Failover happens automatically.
The system disables the bond and uses a single NIC
Why wrong: The bond remains functional.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Traffic automatically switches to the backup NIC with minimal interruption
In bonding mode 1 (active-backup), only one NIC is active at a time while the other remains in standby. When the active NIC fails, the bonding driver automatically fails over to the backup NIC by reassigning the MAC address and IP to the backup interface, typically within a few milliseconds. This ensures minimal interruption to network traffic without requiring manual intervention.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Both NICs continue to pass traffic simultaneously
Why it's wrong here
Only one NIC is active at a time in mode 1.
Traffic automatically switches to the backup NIC with minimal interruption
Why this is correct
Active-backup provides automatic failover.
Related concept
Read the scenario before looking for a memorised answer.
The bond interface goes down until an administrator intervenes
Why it's wrong here
Failover happens automatically.
The system disables the bond and uses a single NIC
Why it's wrong here
The bond remains functional.
Common exam traps
The trap here is that candidates often confuse active-backup (mode 1) with balance-rr (mode 0) or assume that both NICs must be active for redundancy, leading them to incorrectly select Option A.
Detailed technical explanation
Under the hood, bonding mode 1 relies on the bonding driver's ARP monitoring or MII (Media Independent Interface) link monitoring to detect link failures. The failover time depends on the monitoring interval (e.g., miimon=100 for 100 ms checks) and the number of missed link beats before declaring failure. In real-world scenarios, if the switch port fails but the NIC link remains up (e.g., due to a misconfigured VLAN), ARP monitoring is more reliable than MII monitoring for detecting true connectivity loss.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
The correct answer is: Traffic automatically switches to the backup NIC with minimal interruption — In bonding mode 1 (active-backup), only one NIC is active at a time while the other remains in standby. When the active NIC fails, the bonding driver automatically fails over to the backup NIC by reassigning the MAC address and IP to the backup interface, typically within a few milliseconds. This ensures minimal interruption to network traffic without requiring manual intervention.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation 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 LFCS exam.
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