Demo Working with nmcli

In this lesson you’ll learn how to manage network connectivity using nmcli, the command-line tool for NetworkManager. This demo walks through inspecting device status, creating a new Ethernet connection, verifying IP/routing/DNS, modifying addresses, and deleting the connection.

A dark-themed presentation slide with the title "Demo" and the subtitle "Working with nmcli" on the left. A large empty dark rectangle occupies the right side of the slide.

Callouts

Run nmcli commands as root (or with sudo) because most connection operations require privileges. You can inspect system-managed connection files under /etc/NetworkManager/system-connections/.

1. Check current devices and connections

Start by listing device status to discover available interfaces:

root@control:~# nmcli device status
DEVICE  TYPE      STATE      CONNECTION
enp0s3  ethernet  connected  enp0s3
lo      loopback  unmanaged  lo

Then list configured connections and the devices they are bound to:

root@control:~# nmcli connection show
NAME    UUID                                  TYPE      DEVICE
enp0s3  6f9c3bb8-fb17-38d3-93c0-e6cfa258782e  ethernet  enp0s3
lo      a8886d34-a666-4301-9bae-e6d2e7b4eda2  loopback  lo

2. Create a new Ethernet connection

In this example we’ll create a static IPv4 Ethernet connection with these parameters:

type: ethernet
ifname: enp0s3 (interface name)
con-name: custom-connection (human-friendly connection name)
ipv4.addresses: 10.0.2.18/24
ipv4.gateway: 10.0.2.1
ipv4.dns: 8.8.8.8
ipv4.method: manual

Run the add command:

root@control:~# nmcli connection add type ethernet ifname enp0s3 con-name custom-connection ipv4.addresses 10.0.2.18/24 ipv4.gateway 10.0.2.1 ipv4.dns 8.8.8.8 ipv4.method manual
Connection 'custom-connection' (75de3eb2-9883-4dd5-8bac-1b89ee0bb9c5) successfully added.

Verify the connection was created (note the DEVICE column shows -- when not active):

root@control:~# nmcli connection show
NAME                UUID                                  TYPE      DEVICE
enp0s3              6f9c3bb8-fb17-38d3-93c0-e6cfa258782e  ethernet  enp0s3
lo                  a8886d34-a666-4301-9bae-e6d2e7b4eda2  loopback  lo
custom-connection   75de3eb2-9883-4dd5-8bac-1b89ee0bb9c5  ethernet  --

To inspect the connection’s full properties:

root@control:~# nmcli connection show custom-connection

(That command prints the connection’s stored properties, such as IPv4/IPv6 settings, MAC address, autoconnect, and more.)

3. Activate the connection

Bring the connection up:

root@control:~# nmcli connection up custom-connection
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/3)

Then verify the interface has the configured IP address:

root@control:~# ip addr show enp0s3
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 08:00:27:f0:46:06 brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.18/24 brd 10.0.2.255 scope global noprefixroute enp0s3
       valid_lft forever preferred_lft forever
    inet6 fe80::4c93:328c:c333:34cb/64 scope link noprefixroute
       valid_lft forever preferred_lft forever

Confirm the routing table shows the configured gateway:

root@control:~# ip route
default via 10.0.2.1 dev enp0s3 proto static metric 100
10.0.2.0/24 dev enp0s3 proto kernel scope link src 10.0.2.18 metric 100

Check DNS as configured by NetworkManager:

root@control:~# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 8.8.8.8

Do not edit /etc/resolv.conf manually when NetworkManager is managing it — changes may be overwritten. Configure DNS via nmcli or NetworkManager config files if you need persistent edits.

Test connectivity by pinging the DNS server and resolving a hostname:

root@control:~# ping -c 3 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=255 time=17.9 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=255 time=18.1 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=255 time=20.3 ms

--- 8.8.8.8 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2004ms
rtt min/avg/max/mdev = 17.878/18.766/20.288/1.080 ms

root@control:~# ping -c 2 google.com
PING google.com (172.217.17.78) 56(84) bytes of data.
64 bytes from ams16s30-in-f78.1e100.net (172.217.17.78): icmp_seq=1 ttl=255 time=18.3 ms
64 bytes from ams16s30-in-f78.1e100.net (172.217.17.78): icmp_seq=2 ttl=255 time=19.7 ms

4. Modify an existing connection (add a second IPv4 address)

Use nmcli connection modify together with the + operator to append an IPv4 address:

root@control:~# nmcli connection modify custom-connection +ipv4.addresses 10.0.2.19/24

If the connection is active, reapply it to make changes take effect:

root@control:~# nmcli connection up custom-connection
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/3)

Verify both IP addresses are present:

root@control:~# ip addr show enp0s3
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 08:00:27:f0:46:06 brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.18/24 brd 10.0.2.255 scope global noprefixroute enp0s3
       valid_lft forever preferred_lft forever
    inet 10.0.2.19/24 brd 10.0.2.255 scope global secondary noprefixroute enp0s3
       valid_lft forever preferred_lft forever

5. Delete the custom connection

When you no longer need the connection, remove it:

root@control:~# nmcli connection delete custom-connection
Connection 'custom-connection' successfully deleted.

Confirm removal:

root@control:~# nmcli connection show
NAME    UUID                                  TYPE      DEVICE
enp0s3  6f9c3bb8-fb17-38d3-93c0-e6cfa258782e  ethernet  enp0s3
lo      a8886d34-a666-4301-9bae-e6d2e7b4eda2  loopback  lo

Quick reference: common nmcli commands

Task	Command
List device status	`nmcli device status`
List configured connections	`nmcli connection show`
Add a connection	`nmcli connection add type ethernet ifname <iface> con-name <name> ipv4.addresses <addr/mask> ipv4.gateway <gw> ipv4.dns <dns> ipv4.method manual`
Show connection details	`nmcli connection show <con-name>`
Activate a connection	`nmcli connection up <con-name>`
Modify a connection (append)	`nmcli connection modify <con-name> +ipv4.addresses <addr/mask>`
Delete a connection	`nmcli connection delete <con-name>`

Links and references

NetworkManager documentation: https://networkmanager.dev/docs/
nmcli manual: man nmcli
Red Hat NetworkManager guide: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/

This concludes the demo on using nmcli to create, modify, activate, verify, and delete NetworkManager connections.

Introduction

Working with the Command Line

File Management

Working with Text Files

Output Redirection

User Management

Linux Permissions

Enhanced Command Line

Storage Management

Managing Services

Controlling the Boot Process

Scheduling Future Tasks

Working with Logs

Installing Software

Process Management & Tuning

Managing Network Configuration and Security

SELinux

Configuring SSH

Demo Working with nmcli

1. Check current devices and connections

2. Create a new Ethernet connection

3. Activate the connection

4. Modify an existing connection (add a second IPv4 address)

5. Delete the custom connection

Quick reference: common nmcli commands

Links and references

Watch Video

​1. Check current devices and connections

​2. Create a new Ethernet connection

​3. Activate the connection

​4. Modify an existing connection (add a second IPv4 address)

​5. Delete the custom connection

​Quick reference: common nmcli commands

​Links and references

Watch Video

1. Check current devices and connections

2. Create a new Ethernet connection

3. Activate the connection

4. Modify an existing connection (add a second IPv4 address)

5. Delete the custom connection

Quick reference: common nmcli commands

Links and references