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.
An administrator is configuring network bonding on a RHEL 7 server with two physical NICs (eth0 and eth1) to provide redundancy. The bond interface bond0 is configured with mode 1 (active-backup). The administrator uses the following configuration in /etc/sysconfig/network-scripts/ifcfg-bond0: BONDING_OPTS="miimon=100 mode=1". The slave interfaces are configured with MASTER=bond0 and SLAVE=yes. After restarting the network service, the bond interface comes up with the active link on eth0. To test failover, the administrator disconnects the cable from eth0. The bond interface does not fail over to eth1. The administrator checks /proc/net/bonding/bond0 and sees that both slaves are listed but eth0 is still marked as active even though the cable is disconnected. What is the most likely reason for the failover failure?
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
✓
Add arp_interval=1000 and arp_ip_target=192.168.1.1 to BONDING_OPTS.
Option A is correct because in mode 1 (active-backup), the bonding driver uses MII monitoring (miimon) to detect link state changes via the physical carrier signal. However, some switches or NICs do not properly report carrier loss when a cable is disconnected, causing miimon to miss the failure. Adding arp_interval and arp_ip_target forces the bonding driver to use ARP-based monitoring, which actively probes a target IP to verify link availability, thus detecting failures that miimon cannot see.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Add arp_interval=1000 and arp_ip_target=192.168.1.1 to BONDING_OPTS.
Why this is correct
ARP monitoring can detect link failures when MII monitoring fails.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change bonding mode to mode 4 (802.3ad load balancing).
Why it's wrong here
Mode 4 is for load balancing with switch support, not redundancy.
✗
Remove one slave and re-add it to force a failover.
Why it's wrong here
Temporary workaround, not a permanent fix.
✗
Check /var/log/messages for bonding driver errors.
Why it's wrong here
Diagnostic but does not fix the failover issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume miimon always detects physical disconnection, but the exam tests the understanding that carrier detection can fail, requiring ARP monitoring as a fallback for reliable failover.
Detailed technical explanation
How to think about this question
The bonding driver's miimon uses the MII (Media Independent Interface) ioctl to read the carrier status from the NIC driver. Some NICs or switch configurations may keep the carrier signal high even after cable disconnection (e.g., due to switch port keepalive or faulty hardware). ARP monitoring works at a higher layer by sending ARP requests to a configured target and expecting replies; if replies stop, the bond marks the link as down. This is why ARP monitoring is recommended in environments where carrier detection is unreliable.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add arp_interval=1000 and arp_ip_target=192.168.1.1 to BONDING_OPTS. — Option A is correct because in mode 1 (active-backup), the bonding driver uses MII monitoring (miimon) to detect link state changes via the physical carrier signal. However, some switches or NICs do not properly report carrier loss when a cable is disconnected, causing miimon to miss the failure. Adding arp_interval and arp_ip_target forces the bonding driver to use ARP-based monitoring, which actively probes a target IP to verify link availability, thus detecting failures that miimon cannot see.
What should I do if I get this LFCS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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