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LFCS Networking Practice Question

Exhibit

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
    link/ether 52:54:00:12:34:56 brd ff:ff:ff:ff:ff:ff

Refer to the exhibit. The output of 'ip addr show' reveals that eth0 is in state DOWN and has no IPv4 address. Which command is most likely to bring the interface up and obtain an IP via DHCP?

⚠ Common exam trap

Watch out — candidates often assume `ip link set eth0 up` (options A or D) is sufficient to obtain an IP via DHCP, but this command only activates the link layer and does not invoke any DHCP client, leaving the interface without an IP address.

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

✓

ifup eth0

The `ifup` command is a distribution-agnostic tool that reads the interface configuration from files (e.g., `/etc/network/interfaces` on Debian/Ubuntu or `/etc/sysconfig/network-scripts/ifcfg-eth0` on RHEL/CentOS) and brings the interface up while automatically initiating a DHCP client (e.g., dhclient or dhcpcd) to obtain an IPv4 address. This is the standard way to activate a network interface with its configured addressing method, including DHCP, in a single step.

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 link set eth0 up

    Why it's wrong here

    Brings the interface up but DHCP may not automatically start unless configured.

  • ✓

    ifup eth0

    Why this is correct

    ifup invokes the network configuration scripts, which will start DHCP based on config.

  • ✗

    ip route add default via 192.168.1.1 dev eth0

    Why it's wrong here

    Adds a default route but does not bring the interface up or obtain an address.

  • ✗

    ip link set dev eth0 up

    Why it's wrong here

    Same as A; may not trigger DHCP.

Visual reference

Client DHCP Server 1 Discover (broadcast) 2 Offer (IP: 192.168.1.10) 3 Request (I accept) 4 Acknowledge (lease confirmed) DORA — the four-step DHCP lease process

About these practice questions

This LFCS question is part of Courseiva's 507-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →

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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.