LFCS Networking Practice Question
A storage administrator must add a persistent secondary IPv4 address 192.0.2.50/24 to interface eth1 on a RHEL 9 server using NetworkManager. The primary address is already configured. Which command adds the address so that it survives a reboot?
⚠ Common exam trap
The trap here is omitting the + prefix, which silently replaces the existing address list instead of appending to it.
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
✓
nmcli con mod eth1 +ipv4.addresses 192.0.2.50/24 && nmcli con up eth1
On RHEL 9, NetworkManager stores connection profiles, and nmcli con mod edits them persistently. Using the + prefix before ipv4.addresses appends the new address to the existing list, preserving the primary address. Reactivating the connection with nmcli con up applies the change immediately, and the profile ensures the secondary address returns after a reboot.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ip addr add 192.0.2.50/24 dev eth1
Why it's wrong here
This adds the address to the running kernel immediately, but the change is not recorded in NetworkManager's connection profile, so it disappears on reboot or when the interface is brought down. It is useful for temporary testing but does not meet the persistence requirement. The administrator would need to also modify the connection profile.
- ✗
echo 'IPADDR1=192.0.2.50' >> /etc/sysconfig/network-scripts/ifcfg-eth1 && systemctl restart network
Why it's wrong here
RHEL 9 uses NetworkManager with keyfiles by default, and the legacy network service is not present. Writing to ifcfg-eth1 does not update the active NetworkManager profile, and systemctl restart network would fail because the network service does not exist. This approach is obsolete and does not achieve persistence on RHEL 9.
- ✓
nmcli con mod eth1 +ipv4.addresses 192.0.2.50/24 && nmcli con up eth1
Why this is correct
The nmcli con mod command with the + prefix appends the address to the existing ipv4.addresses list in the connection profile, preserving the primary address. Running nmcli con up reactivates the connection and applies the change. Because the profile is stored persistently, the secondary address is restored on reboot, satisfying the requirement.
- ✗
nmcli con mod eth1 ipv4.addresses 192.0.2.50/24 && nmcli con up eth1
Why it's wrong here
Without the + prefix, this replaces the entire ipv4.addresses value, removing the existing primary address. The interface would come up with only 192.0.2.50/24, which breaks connectivity that depended on the original address. The administrator must use the append syntax to add a secondary address without discarding the primary.
Go deeper
Related to this question
About these practice questions
Courseiva writes every LFCS question from scratch — 406 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Linux Foundation exam blueprint
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.