The nmcli connection show command can be used to list your network interfaces.

~]# nmcli connection show
NAME  UUID                                  TYPE      DEVICE 
eth0  5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03  ethernet  eth0

Specifying a connection will show the settings for the connection.

]# nmcli connection show eth0 | grep -i ipv4
ipv4.method:                            manual
ipv4.dns:                               10.11.12.13,10.11.12.14
ipv4.dns-search:                        example.com
ipv4.dns-options:                       timeout:2
ipv4.dns-priority:                      0
ipv4.addresses:                         10.11.12.15/22
ipv4.gateway:                           10.0.0.1
ipv4.routes:                            --
ipv4.route-metric:                      -1
ipv4.route-table:                       0 (unspec)
ipv4.routing-rules:                     --
ipv4.replace-local-rule:                -1 (default)
ipv4.ignore-auto-routes:                no
ipv4.ignore-auto-dns:                   no
ipv4.dhcp-client-id:                    --
ipv4.dhcp-iaid:                         --
ipv4.dhcp-timeout:                      0 (default)
ipv4.dhcp-send-hostname:                yes
ipv4.dhcp-hostname:                     --
ipv4.dhcp-fqdn:                         --
ipv4.dhcp-hostname-flags:               0x0 (none)
ipv4.never-default:                     no
ipv4.may-fail:                          yes
ipv4.required-timeout:                  -1 (default)
ipv4.dad-timeout:                       -1 (default)
ipv4.dhcp-vendor-class-identifier:      --
ipv4.link-local:                        0 (default)
ipv4.dhcp-reject-servers:               --
ipv4.auto-route-ext-gw:                 -1 (default)

Likewise, the ip address command should show the IP address bound to the interface.

~]# ip address | grep inet
    inet 10.11.12.15/22 brd 10.1.2.3 scope global noprefixroute eth0

The nmcli connection modify <interface name> command can be used to add one or more secondary IP addresses to the interface.

nmcli connection modify eth0 +ipv4.addresses 10.11.12.16/22

Now, the nmcli connection show command should show the secondary IP addresses that were added.

]# nmcli connection show eth0 | grep -i ipv4.addresses
ipv4.addresses:                         10.11.12.15/22, 10.11.12.16/22

But the ip address command should not yet include the secondary IP addresses.

~]# ip address show eth0 | grep inet
    inet 10.11.12.15/22 brd 10.1.2.3 scope global noprefixroute eth0

The nmcli device reapply <interface name> command must be used for this change to take effect on the interface.

]# nmcli device reapply eth0
Connection successfully reapplied to device 'eth0'.

But the ip address command should not yet include the secondary IP addresses.

~]# ip address | grep inet
    inet 10.11.12.15/22 brd 10.1.2.3 scope global noprefixroute eth0
    inet 10.11.12.16/22 brd 10.1.2.3 scope global secondary noprefixroute eth0