LFCS Networking Practice Question
A system administrator needs to configure bonding in active-backup mode. Which line in /etc/sysconfig/network-scripts/ifcfg-bond0 defines the bonding mode and primary interface?
⚠ Common exam trap
The trap is that candidates may assume only numeric mode values are correct, but many Linux distributions accept both numeric (mode=1) and textual (mode=active-backup) representations. Both are valid for active-backup bonding mode.
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
✓
BONDING_OPTS="mode=1 primary=eth0 miimon=100"
Options A and B are both correct. Both lines use BONDING_OPTS to set the bonding mode and primary interface. Option A uses the numeric mode value 'mode=1', which is the standard numeric representation for active-backup. Option B uses the textual value 'mode=active-backup', which is also valid in many Linux distributions (e.g., RHEL/CentOS). Both include the primary interface (eth0) and the miimon parameter. Options C and D are incorrect because option C uses mode=0 (round-robin) and lacks miimon, and option D omits the primary interface specification.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
BONDING_OPTS="mode=1 primary=eth0 miimon=100"
Why this is correct
Correct. This line uses the numeric mode value '1' for active-backup, which is a standard format. It explicitly defines the primary interface (eth0) and includes the miimon parameter.
- ✓
BONDING_OPTS="miimon=100 mode=active-backup primary=eth0"
Why this is correct
Correct. This line uses the textual mode name 'active-backup', which is also a recognized value in bonding configuration. It sets the primary interface and miimon, meeting the requirement.
- ✗
BONDING_OPTS="mode=0 primary=eth0"
Why it's wrong here
Incorrect. Mode 0 corresponds to round-robin (balance-rr), not active-backup. Additionally, it lacks the miimon parameter.
- ✗
BONDING_OPTS="mode=active-backup miimon=100"
Why it's wrong here
Incorrect. Although it sets mode=active-backup and miimon, it does not specify a primary interface, which is required to define the primary interface.
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