When you install CentOS, RHEL, or OEL with graphical Interface, it comes with NetworkManager. The NetworkManager daemon maks networking configuration and operation easy and automatic as possible by managing network interfaces, either Ethernet, WiFi, or Mobile Broadband devices. Besides, NetworkManager provides a rich API to control network settings and operations. However, when configuring servers It’s preferable to have their networking settings to be consistent. therefore, This article explains how to disable NetworkManager, hence, configure the network and set IP ethernet manually.
The following steps are suitable for versions 6 and 7 of RHEL, OEL, and CentOS.
Firstly, Identify which card you want to configure by executing the ifconfig command with parameter -s to shortlist the output.
[root@s59 ~]# ifconfig -s Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg eno1 1500 4596894 0 5617 0 41057 0 0 0 BMRU lo 65536 440 0 0 0 440 0 0 0 LRU virbr0 1500 0 0 0 0 0 0 0 0 BMU [root@s59 ~]#
In view of the output of our example, you can see that the server has three network interfaces, as follow:
|eno1||LAN Network interface|
|virbr0||Wireless Network interface|
In our case, LAN Interface eno1 is our target.
Firstly, Stop NetworkManager by stopping its service.
systemctl stop NetworkManager.service
Secondly, disable Network Manager using the following command.
systemctl disable NetworkManager.service
manually configure network setting.
Initially, navigate into the network configuration directory. then, edit the configuration file for the ethernet. For example, if the card name eno1 then the filename is ifcfg-eno1.
vi / etc/sysconfig/network-scripts/ifcfg-eno1
After that, add the following parameters in the file if they are not exist
ONBOOT=yes NM_CONTROLLED=no BOOTPROTO=none IPADDR=XXX.XXX.XXX.XXX NETMASK=255.255.255.0 # you can use PREFIX=24 instead of NETMASK=255.255.255.0 GATEWAY=<GATE WAY IP XXX.XXX.XXX.XXX>
Optional you can add the following lines to force DNS on specific Card
DNS1=<DNS IP XXX.XXX.XXX.XXX> DNS2=<DNS IP XXX.XXX.XXX.XXX>
Manually configure DNS resolve file.
make sure it has a reliable DNS IPs, for example, google public DNS 126.96.36.199
vi /etc/resolv.conf nameserver 188.8.131.52
Finally, type :wq to save & exit the editor.
Restart network services
For version 6, use the service command.
# Service restart network
On RHEL 7 use systemD command, though, executing the above command will redirect to systemD command
# systemctl restart network.service