On Sat, Jan 22, 2011 at 1:29 AM, Ritika Garg <ritikagarg25 at gmail.com> wrote: > I pressed the tab "probe" by mistake near "bind to MAC address" in > system->administration->network->edit->hardware device. After this the MAC > address disappeared. Internet is not working. Shall I write the MAC address > and activate again? That will *probably* work. But NetworkManager and its utilities are *NOT* your friend. Learn to directly edit /etc/sysconfig/network-scripts/ifcfg-* files. You will find features that NetworkManager does not support, at least in RHEL 5, such as setting the "SEARCH=" option for DHCP configurations or pair-bonding or setting up network bridges for KVM use. And you can handle backups much more consistently.