Basics Of NetworkManager Command Line Tool, Nmcli

By
Rajneesh Upadhyay

Introduction

In this tutorial, we will discuss NetworkManager command line tool, aka nmcli, in CentOS / RHEL 7. Users who are using ifconfig should avoid this command in Centos 7.

Lets configure some networking settings with nmcli utility.

To get all address information of all interfaces connected with System

[root@localhost ~]# ip addr show

Sample Output:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
 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
 inet6 ::1/128 scope host 
 valid_lft forever preferred_lft forever
2: eno16777736: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
 link/ether 00:0c:29:67:2f:4c brd ff:ff:ff:ff:ff:ff
 inet 192.168.1.51/24 brd 192.168.1.255 scope global eno16777736
 valid_lft forever preferred_lft forever
 inet6 fe80::20c:29ff:fe67:2f4c/64 scope link 
 valid_lft forever preferred_lft forever

To retrieve packets statistics related with connected interfaces

[root@localhost ~]# ip -s link show eno16777736

Sample Output:

unxmen_(011)

Get routing configuration

[root@localhost ~]# ip route

Sample Output:

default via 192.168.1.1 dev eno16777736 proto static metric 100 
192.168.1.0/24 dev eno16777736 proto kernel scope link src 192.168.1.51 metric 100

Analyze path for some host/website

[root@localhost ~]# tracepath unixmen.com

Output will be just like traceroute but in more managed form.

unxmen_0121

nmcli utility

Nmcli is a very rich and flexible command line utility. some of the terms used in nmcli are:

  • Device – A network interface being used.
  • Connection – A set of configuration settings, for a single device you can have multiple connections, you can switch between connections.

Find out how many connections are available for how many devices

[root@localhost ~]# nmcli connection show

unxmen_(013)

Get details of a specific connection

[root@localhost ~]# nmcli connection show eno1

Sample output:

unxmen_(014)

Get the Network device status

[root@localhost ~]# nmcli device status
 DEVICE               TYPE              STATE          CONNECTION 
eno16777736            ethernet      connected              eno1 
lo                     loopback      unmanaged               --

Create a new connection with “dhcp”

[root@localhost ~]# nmcli connection add con-name "dhcp" type ethernet ifname eno16777736

Where,

  • Connection add – To add new connection
  • con-name – connection name
  • type – type of device
  • ifname – interface name

This command will add connection with dhcp protocol.

Sample output:

Connection 'dhcp' (163a6822-cd50-4d23-bb42-8b774aeab9cb) successfully added.

Instead of assigning an IP via dhcp, you can add ip address as “static”

[root@localhost ~]# nmcli connection add con-name "static" ifname eno16777736 autoconnect no type ethernet ip4 192.168.1.240 gw4 192.168.1.1

Sample Output:

Connection 'static' (8e69d847-03d7-47c7-8623-bb112f5cc842) successfully added.

Update connection:

[root@localhost ~]# nmcli connection up eno1

Again Check, whether ip address is changed or not.

[root@localhost ~]# ip addr show

unxmen_(015)

Add DNS settings to Static connections.

[root@localhost ~]# nmcli connection modify "static" ipv4.dns 202.131.124.4

Add additional DNS value.

[root@localhost ~]# nmcli connection modify "static" +ipv4.dns 8.8.8.8

Note: For additional entries + symbol will be used and +ipv4.dns will be used instead on ip4.dns

Put an additional ip address:

[root@localhost ~]# nmcli connection modify "static" +ipv4.addresses 192.168.200.1/24

Refresh settings using command:

[root@localhost ~]# nmcli connection up eno1

unxmen_(016)

You will see, setting are effective now.

That’s it.