LFCS Networking Practice Question
A system administrator wants to combine two network interfaces for increased throughput and fault tolerance. The requirement is that both links are active simultaneously and the system can tolerate a failure of one link without interruption. Which bonding mode should be used?
⚠ Common exam trap
Many candidates confuse Mode 4 (802.3ad) with Mode 0 (balance-rr) because both allow active links, but Mode 0 lacks the standardized LACP negotiation and seamless failover that Mode 4 provides, leading to incorrect selection when fault tolerance is explicitly required.
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
✓
Mode 4 (802.3ad)
Mode 4 (802.3ad) is correct because it implements IEEE 802.3ad Link Aggregation Control Protocol (LACP), which allows both links to be active simultaneously for increased throughput while providing fault tolerance. If one link fails, traffic is automatically redistributed across the remaining active links without interruption, meeting the requirement for both active links and failure tolerance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Mode 4 (802.3ad)
Why this is correct
Mode 4 (802.3ad) is correct because it implements IEEE 802.3ad Link Aggregation Control Protocol (LACP), which allows both links to be active simultaneously for increased throughput while providing fault tolerance. If one link fails, traffic is automatically redistributed across the remaining active links without interruption, meeting the requirement.
- ✗
Mode 2 (balance-xor)
Why it's wrong here
Mode 2 (balance-xor) does provide fault tolerance by automatically redistributing traffic to remaining links on failure, but its load distribution is based on XOR of MAC addresses and may not fully aggregate bandwidth across both links. Additionally, it does not use the standardized LACP protocol, which is typically required for proper link aggregation.
- ✗
Mode 1 (active-backup)
Why it's wrong here
Mode 1 keeps one slave dormant as a standby, so only a single link carries traffic at any moment and aggregate throughput is not increased. It is tempting because failover works transparently, but active-backup is the right choice when redundancy alone is required and the switch cannot support link aggregation.
- ✗
Mode 0 (balance-rr)
Why it's wrong here
Mode 0 distributes frames round-robin across slaves, but it provides no failure detection or failover; losing one link breaks or degrades the bond. It is tempting because both links are active and throughput rises, but balance-rr suits scenarios where switch support and link stability are assured and fault tolerance is not required.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.