Invoking GUI Network tool on Centos 6

 nm-connection-editor

you need to first install NetworkManager using YUM

yum install NetworkManager

Or check it is already started or not

service NetworkManager status

else start the service

service NetworkManager start
chkconfig NetworkManager on

To open to GUI interface you need to execute “nm-applet” command. and to configure or edit configurations “nm-connection-editor” use this command

nm-applet
nm-connection-editor (note: this command is formerly known as system-config-network-gui)