LFCS Networking Practice Question
A technician configured a new network interface eth1 on a CentOS 7 server but the interface does not obtain an IPv4 address via DHCP. Which of the following is the most likely cause?
⚠ Common exam trap
Many exam-takers assume firewall or SELinux is the culprit for DHCP failures, but the most common cause on CentOS 7 is the NM_CONTROLLED=no setting, which disables NetworkManager's DHCP client management.
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
✓
NetworkManager is not managing the interface (NM_CONTROLLED=no)
When NM_CONTROLLED=no is set in the interface configuration file (/etc/sysconfig/network-scripts/ifcfg-eth1), NetworkManager will not manage that interface. Since dhclient is typically invoked by NetworkManager (or by legacy network scripts only if NM_CONTROLLED=yes), the interface will not automatically obtain an IPv4 address via DHCP. On CentOS 7, NetworkManager is the default network service, and disabling its control prevents DHCP client activation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The interface MTU is set too high
Why it's wrong here
MTU mismatch does not prevent DHCP discovery.
- ✗
SELinux is blocking dhclient
Why it's wrong here
SELinux does not block dhclient by default.
- ✓
NetworkManager is not managing the interface (NM_CONTROLLED=no)
Why this is correct
When NM_CONTROLLED=no, NetworkManager ignores the interface, so DHCP is not attempted.
- ✗
Firewalld is blocking DHCP ports (67/68)
Why it's wrong here
Firewalld usually allows DHCP by default.
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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.