Linux+ Network Interface Configuration Questions and Answers

Question 1

A system administrator needs to add a secondary IP address, 10.0.1.150/24, to an existing network interface named `ens192` which is managed by NetworkManager. The change must be applied without deactivating the interface. Which of the following commands correctly accomplishes this?

Accepted Answer

nmcli con modify ens192 +ipv4.addresses 10.0.1.150/24

Answer

The `nmcli con modify` command is used to alter an existing NetworkManager connection profile. The key is using the `+` prefix before `ipv4.addresses` to append a new address to the list of existing addresses. Without the `+`, the command would replace all existing IP addresses with the new one.

Question 2

An administrator is configuring a new Ubuntu server that uses Netplan for network configuration. To assign a static IP address, which file would they MOST likely create or edit?

Accepted Answer

/etc/netplan/01-netcfg.yaml

Answer

Modern Ubuntu systems use Netplan for network configuration, with YAML files located in `/etc/netplan/`. A file like `/etc/netplan/01-netcfg.yaml` is the standard location for defining network interfaces, including static IP addresses.

Question 3

A network interface `enp0s8` on a Linux server is currently in a 'DOWN' state. Which of the following commands is the modern and direct way to bring the interface to an 'UP' state?

Accepted Answer

ip link set enp0s8 up

Answer

The `ip link set <interface> up` command is the standard and modern utility from the iproute2 suite used to change the state of a network device, specifically to bring it online. While other commands might work in certain contexts, this is the most direct and fundamental command for the task.

Question 4

A server is unable to resolve any external domain names (e.g., www.google.com), but it can ping IP addresses on the internet (e.g., 8.8.8.8). Which file should the administrator check FIRST to troubleshoot this name resolution issue?

Accepted Answer

/etc/resolv.conf

Answer

The `/etc/resolv.conf` file contains the IP addresses of the DNS nameservers the system uses to resolve domain names. If this file is empty, misconfigured, or points to non-functional nameservers, the system will be unable to resolve domain names, matching the symptoms described.

Question 5

A Linux server needs a persistent static route added. All traffic destined for the `172.16.50.0/24` network must be sent through the gateway at `10.1.1.254`. On a RHEL/CentOS system using traditional network scripts, what is the proper way to add this route permanently?

Accepted Answer

Create a file `/etc/sysconfig/network-scripts/route-eth0` with the content `172.16.50.0/24 via 10.1.1.254`

Answer

On RHEL-family systems using traditional network scripts, persistent static routes are defined in a `route-<interface>` file located in `/etc/sysconfig/network-scripts/`. The format `ADDRESS/PREFIX via GATEWAY` within this file ensures the route is applied when the interface is brought up.

Linux Practice Test

Linux Practice Test

Linux+ Network Interface Configuration Questions and Answers