There could be a multiple reason for nmcli Error: unknown connection. In this tutorial I am going to fix the unknown connection issue during the IP addess configuration on a device.
If you are facing issue when you are trying to configure network for a device in Linux OS. Please follow below steps to fix the same.
Let’s check the current active IP address of system.
[root@TechArticles ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
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: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 08:00:27:e5:4f:ea brd ff:ff:ff:ff:ff:ff
inet 192.168.111.77/24 brd 192.168.111.255 scope global dynamic noprefixroute enp0s3
valid_lft 3491sec preferred_lft 3491sec
inet6 2409:4089:8214:b7e0:a00:27ff:fee5:4fea/64 scope global dynamic noprefixroute
valid_lft 3548sec preferred_lft 3548sec
inet6 fe80::a00:27ff:fee5:4fea/64 scope link noprefixroute
valid_lft forever preferred_lft forever
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 08:00:27:c2:15:90 brd ff:ff:ff:ff:ff:ff
4: enp0s9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 08:00:27:77:43:28 brd ff:ff:ff:ff:ff:ff
5: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP>mtu 1500 qdisc noqueue state DOWN group default qlen 1000
link/ether 52:54:00:8b:26:aa brd ff:ff:ff:ff:ff:ff
inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
valid_lft forever preferred_lft forever
As per above Interface details, I am going to configure IP on enp0s8 interface. In your case it may be different device name.
As per above device details, you can see device enp0s8 is available and there is no IP assigned.
I am going to configure below IP on device enp0s8.
IP address: 192.168.111.100/24 Default gateway: 192.168.111.100 Preferred DNS: 8.8.8.8 IP addressing static
Let’s check the device details by running nmcli device status command.
[root@TechArticles ~]# nmcli device status DEVICE TYPE STATE CONNECTION enp0s3 ethernet connected enp0s3 virbr0 bridge connected (externally) virbr0 enp0s8 ethernet disconnected -- enp0s9 ethernet disconnected -- lo loopback unmanaged --
As you can see enp0s8 ethernet is showing disconnected.
Let’s configre IP address for device enp0s8.
[root@TechArticles ~]# nmcli con mod enps08 ipv4.addresses 192.168.111.100/24 Error: unknown connection 'enps08'. [root@TechArticles ~]#
Now, you can see device is available but its says Error: unknown connection 'enps08'.
Basicly this is not a nmcli error, it is throwing error just beacuse the device is available but there is no connection created for device enp0s8.
We can check connection by running below command.
[root@TechArticles ~]# nmcli con show NAME UUID TYPE DEVICE enp0s3 b972dea7-b72d-4e48-a838-bda20615e189 ethernet enp0s3 virbr0 58bed60d-b638-4e39-978d-5417bee137dc bridge virbr0
As per above command output device enp0s8 is not available, So we have to create the connection first for device enp0s8. Then we will be able to configure IP for it.
If you can see your device after running the above command, then stop here and please continue reading How to fix nmcli connection up Error: unknown connection issue in Linux CentOS/RHEL; If not, proceed to the steps to resolve the issue below.
Follow below stpes to create the connection for device enp0s8
[root@TechArticles ~]# nmcli connection add type ethernet connection.interface-name enp0s8 con-name enp0s8 Connection 'enp0s8' (14cb1621-2a4a-47f6-8092-3323e7cb4e65) successfully added. [root@TechArticles ~]# nmcli con show NAME UUID TYPE DEVICE enp0s3 b972dea7-b72d-4e48-a838-bda20615e189 ethernet enp0s3 enp0s8 14cb1621-2a4a-47f6-8092-3323e7cb4e65 ethernet enp0s8 virbr0 58bed60d-b638-4e39-978d-5417bee137dc bridge virbr0
As you can see that device enp0s8 is now available in connecion list. Let’s move further to configure the IP. This time we will not get any error.
[root@TechArticles ~]# nmcli connection modify enp0s8 ipv4.addresses 192.168.111.77/24
Assign the gateway.
[root@TechArticles ~]# nmcli connection modify enp0s8 ipv4.gateway 192.168.111.1
Assign the DNS server IP.
[root@TechArticles ~]# nmcli con mod enp0s8 ipv4.dns "8.8.8.8"
Then change the connection status from auto to manual and enable the interface at boot.
[root@TechArticles ~]# nmcli con mod enp0s8 ipv4.method manual [root@TechArticles ~]# nmcli con mod enp0s8 autoconnect yes
To save the changes, run the command.
[root@TechArticles ~]# nmcli con up enp0s8
Then verify if the IP is configured or not to interface
[root@TechArticles ~]# ip addr show dev enp0s8
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 08:00:27:c2:15:90 brd ff:ff:ff:ff:ff:ff
inet 192.168.111.100/24 brd 192.168.111.255 scope global dynamic noprefixroute enp0s8
valid_lft 560sec preferred_lft 560sec
inet6 fe80::6618:b371:6916:184b/64 scope link noprefixroute
valid_lft forever preferred_lft forever
All above changed will be wrriten in /etc/sysconfig/network-scripts/ifcfg-enp0s8 file.
You can view the details of /etc/sysconfig/network-scripts/ifcfg-enp0s8 by running below command.
[root@TechArticles ~]# cat /etc/sysconfig/network-scripts/ifcfg-enp0s8 TYPE=Ethernet PROXY_METHOD=none BROWSER_ONLY=no BOOTPROTO=none 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=enp0s8 UUID=14cb1621-2a4a-47f6-8092-3323e7cb4e65 DEVICE=enp0s8 ONBOOT=yes IPADDR=192.168.111.100 PREFIX=24 GATEWAY=192.168.111.1 DNS1=8.8.8.8
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