Networking Concepts (in RHEL 7 or CENTOS7)

Should concentrate on these if servers upgrade:

  • We usually edit the network configuration file in the older versions to manage IPs.
  • under /etc/sysconfig/network-scripts/
  • In the new version no more editing is required. We can add, modify, delete the IPs using the tool called NMCLI (Network Manager Command Line Interface)
  • You can find the existing ethernet connections by using the following command

#nmcli connection show

Example :- The result will be

NAME UUID TYPE DEVICE
ens3 71697b55-cf9d-42c6-ba4d-bb0c01ae34d9 802-3-ethernet —

You can configure a ethernet connection for Ip4.

#nmcli connection add con-name "static" ifname ens3 type ethernet autoconnect no ip4 172.25.25.25/24 gw4 172.25.254.254

Note:-If you do not want to autoconnect, then you have to manually add "autoconnect no" orelse it is not required.

The result will be:-

NAME UUID TYPE DEVICE
static 6002793c-ad58-424e-a40d-36f647a5bcc6 802-ens3 3-ethernet
ens3 71697b55-cf9d-42c6-ba4d-bb0c01ae34d9 802- 3-ethernet —

To add additional IP to the connection static, we no need to edit it.

#nmcli connection mod "static" +ipv4.addresses 172.25.32.28

  • Above will add the IP to the existing static connection.
  • To bring up the connection

#nmcli connection up static

  • To add a DNS you can also use the following command to the existing connection.

#nmcli connection modify "static" ipv4.dns 8.8.8.8

  • Note : Note that this will replace any previously set DNS servers.
  • To add an additional DNS, simply add +

#nmcli connection modify "static" +ipv4.dns 4.4.4.4

  • Above will not replace the DNS instead it appends.