How to Manage Network through nmcli in CentOS and RHEL

How to Manage Network through nmcli in CentOS and RHEL

nmcli stands for network manager command line interface. As the name suggest you manage the Network through the nmcli command. Let check that out.

1. When you type "nmcli" without any switch it'll show you the existing network information.

[root@exampleserver ~]# nmcli
bond0: connected to bond0
        "bond0"
        bond, B8:2A:72:D5:9D:8L, sw, mtu 1500
        inet4 10.196.100.25/22
        inet6 fe80::ba2a:72ff:fed6:8d8L/64
em1: connected to em1
        "Broadcom Limited NetXtreme BCM5720 Gigabit Ethernet PCIe"
        ethernet (tg3), B8:2A:72:D5:9D:8L, hw, mtu 1500
        master bond0
em2: connected to em2
        "Broadcom Limited NetXtreme BCM5720 Gigabit Ethernet PCIe"
        ethernet (tg3), B8:2A:72:D5:9D:8L, hw, mtu 1500
        master bond0

"nmcli connection show" will show you Name, UUID, TYPE and Device details.

[root@exampleserver ~]# nmcli connection show
NAME         UUID                                  TYPE            DEVICE
bond0        9e0ca102-1bf8-4789-bcf3-38e8bfafa1ba  bond            bond0
bond1        175e3ed5-371c-46a0-99a8-b4ead1b55acd  bond            bond1
em1          71023955-4ffc-4d1d-9f12-d9dccb03d773  802-3-ethernet  em1
em2          b11498L4-cc61-4366-a7bd-cec968be9e20  802-3-ethernet  em2

2. "nmcli device show" Will show you the device details.

[root@exampleserver ~]# nmcli device show
GENERAL.DEVICE:                         bond0
GENERAL.TYPE:                           bond
GENERAL.HWADDR:                         B8:2A:72:D5:9D:8L
GENERAL.MTU:                            1500
GENERAL.STATE:                          100 (connected)
GENERAL.CONNECTION:                     bond0
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/2
IP4.ADDRESS[1]:                         10.196.100.25/22
IP4.GATEWAY:                            10.196.107.254
IP4.DNS[1]:                             10.243.79.10
IP6.ADDRESS[1]:                         fe80::ba2a:72ff:fed6:8d8l/64
IP6.GATEWAY:                            --

3. "nmcli monitor" : Will Observe NetworkManager activity.

4. "nmcli general" and "nmcli general status" will show you the Network Manager status.

[root@exampleserver ~]# nmcli general
STATE      CONNECTIVITY  WIFI-HW  WIFI     WWAN-HW  WWAN
connected  full          enabled  enabled  enabled  enabled
[root@exampleserver ~]# nmcli general status
STATE      CONNECTIVITY  WIFI-HW  WIFI     WWAN-HW  WWAN
connected  full          enabled  enabled  enabled  enabled
[root@exampleserver ~]#

5. nmcli networking {on | off} will Enable or disable networking control by NetworkManager.

6. How to Down or UP the device.

[root@exampleserver ~]# nmcli connection
NAME         UUID                                  TYPE            DEVICE
bond0        9e0ca102-1bf8-4789-bcf3-38e8bfafa1ba  bond            bond0
bond1        175e3ed5-371c-46a0-99a8-b4ead1b55acd  bond            bond1 --> bond1 is UP
em1          71023955-4ffc-4d1d-9f12-d9dccb03d773  802-3-ethernet  em1
em2          b11498L4-cc61-4366-a7bd-cec968be9e20  802-3-ethernet  em2
em3          541237b3-dbe5-4ce4-b3d1-63c9e524ad25  802-3-ethernet  em3
em4          4bed9c3c-d30f-4ccf-adba-1923e2449ef3  802-3-ethernet  em4

[root@exampleserver ~]# nmcli connection down bond1
Connection 'bond1' successfully deactivated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/1)
[root@exampleserver ~]# nmcli connection
NAME         UUID                                  TYPE            DEVICE
bond0        9e0ca102-1bf8-4789-bcf3-38e8bfafa1ba  bond            bond0
em1          71023955-4ffc-4d1d-9f12-d9dccb03d773  802-3-ethernet  em1
em2          b11498L4-cc61-4366-a7bd-cec968be9e20  802-3-ethernet  em2
em3          541237b3-dbe5-4ce4-b3d1-63c9e524ad25  802-3-ethernet  em3
bond1        175e3ed5-371c-46a0-99a8-b4ead1b55acd  bond            -- --> bond1 is Down
em4          4bed9c3c-d30f-4ccf-adba-1923e2449ef3  802-3-ethernet  --
[root@exampleserver ~]#

7. Now UP that device.

[root@exampleserver ~]# nmcli connection up bond1
Connection successfully activated (master waiting for slaves) (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/7)
[root@exampleserver ~]# nmcli connection
NAME         UUID                                  TYPE            DEVICE
bond0        9e0ca102-1bf8-4789-bcf3-38e8bfafa1ba  bond            bond0
bond1        175e3ed5-371c-46a0-99a8-b4ead1b55acd  bond            bond1 --> bond1 is UP
em1          71023955-4ffc-4d1d-9f12-d9dccb03d773  802-3-ethernet  em1
em2          b11498L4-cc61-4366-a7bd-cec968be9e20  802-3-ethernet  em2
em3          541237b3-dbe5-4ce4-b3d1-63c9e524ad25  802-3-ethernet  em3
em4          4bed9c3c-d30f-4ccf-adba-1923e2449ef3  802-3-ethernet  --
[root@exampleserver ~]#

8. Lets Create a Ethernet Connection.

[root@dockerserver ~]# nmcli con add type ethernet con-name test ifname enp0s8
Connection 'test' (4aebc6ae-2e71-426c-8476-681958c34729) successfully added.
type --> Conncation TYPE "ethernet"
con-name --> Conncation name "test"
[root@dockerserver ~]# nmcli c s  ---> C --> Conncation S --> Show
NAME                UUID                                  TYPE            DEVICE
Wired connection 1  d2b72117-f251-37dc-bcba-b427bfb0d21f  802-3-ethernet  enp0s8
br-424cd8d15801     58801a82-9fd4-4a0e-923d-4b4f805d75cc  bridge          br-424cd8d15801
docker0             a7d14ee5-1f9d-4ca1-a5a1-eed61fe12929  bridge          docker0
docker_gwbridge     a5656f9b-43a8-4cf4-9223-1d39ab8b2e85  bridge          docker_gwbridge
enp0s3              7880b9a1-0878-4e8c-b842-160a6432e2ca  802-3-ethernet  enp0s3
test                4aebc6ae-2e71-426c-8476-681958c34729  802-3-ethernet  --   --> Conncation named test created but not active
[root@dockerserver ~]#

9. Now Chceck the config file that has been created now.

[root@dockerserver ~]# cat /etc/sysconfig/network-scripts/ifcfg-test
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=dhcp   --> Default value
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=test
UUID=4aebc6ae-2e71-426c-8476-681958c34729
DEVICE=enp0s8
ONBOOT=yes

10. Check If the interface enp0s8 has pick up the IP or not.

[root@dockerserver ~]# nmcli con show -a  ---> it'l show only active Interface
NAME                UUID                                  TYPE            DEVICE
Wired connection 1  d2b72117-f251-37dc-bcba-b427bfb0d21f  802-3-ethernet  enp0s8
br-424cd8d15801     58801a82-9fd4-4a0e-923d-4b4f805d75cc  bridge          br-424cd8d15801
docker0             a7d14ee5-1f9d-4ca1-a5a1-eed61fe12929  bridge          docker0
docker_gwbridge     a5656f9b-43a8-4cf4-9223-1d39ab8b2e85  bridge          docker_gwbridge
enp0s3              7880b9a1-0878-4e8c-b842-160a6432e2ca  802-3-ethernet  enp0s3
[root@dockerserver ~]# nmcli con down "Wired connection 1"
Connection 'Wired connection 1' successfully deactivated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/2)
[root@dockerserver ~]#
[root@dockerserver ~]# nmcli con up test
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/7)
[root@dockerserver ~]# nmcli con show
NAME                UUID                                  TYPE            DEVICE
br-424cd8d15801     58801a82-9fd4-4a0e-923d-4b4f805d75cc  bridge          br-424cd8d15801
docker0             a7d14ee5-1f9d-4ca1-a5a1-eed61fe12929  bridge          docker0
docker_gwbridge     a5656f9b-43a8-4cf4-9223-1d39ab8b2e85  bridge          docker_gwbridge
enp0s3              7880b9a1-0878-4e8c-b842-160a6432e2ca  802-3-ethernet  enp0s3
test                4aebc6ae-2e71-426c-8476-681958c34729  802-3-ethernet  enp0s8 --> test is active now
Wired connection 1  d2b72117-f251-37dc-bcba-b427bfb0d21f  802-3-ethernet  --
[root@dockerserver ~]#
[root@dockerserver ~]# ip addr show enp0s8
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 08:00:27:89:f1:73 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.101/24 brd 192.168.1.255 scope global dynamic enp0s8
       valid_lft 85955sec preferred_lft 85955sec
    inet6 fe80::a61d:5b39:b681:1a37/64 scope link
       valid_lft forever preferred_lft forever

11. No IP details are there in the config as boot protocol is DHCP. Lets add a static ip.
a. Lets First delete the profile "test", its not mandatory. You can choose another name aswell to segregate the profile.

[root@dockerserver ~]# nmcli conn del test
Connection 'test' (4aebc6ae-2e71-426c-8476-681958c34729) successfully deleted.
[root@dockerserver ~]#
b. [root@dockerserver ~]# nmcli con add type ethernet con-name test ifname enp0s8 ip4 192.168.1.111/24 gw4 192.168.1.1
Connection 'test' (1b88b270-ef07-460c-90c3-830ccdf39a74) successfully added.
[root@dockerserver ~]#
[root@dockerserver ~]# ip addr show enp0s8
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 08:00:27:89:f1:73 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.111/24 brd 192.168.1.255 scope global enp0s8
       valid_lft forever preferred_lft forever
    inet6 fe80::d004:404b:1c76:63a9/64 scope link
       valid_lft forever preferred_lft forever
[root@dockerserver ~]#

12. Now modify and add DNS server information to this profile test

[root@dockerserver ~]# nmcli con mod test ipv4.dns '10.243.79.10 8.8.8.8'
[root@dockerserver ~]#  cat /etc/sysconfig/network-scripts/ifcfg-test
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
IPADDR=192.168.1.111
PREFIX=24
GATEWAY=192.168.1.1
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=test
UUID=1b88b270-ef07-460c-90c3-830ccdf39a74
DEVICE=enp0s8
ONBOOT=yes
DNS1=10.243.79.10
DNS2=8.8.8.8
[root@dockerserver ~]#