Note to self: -
If you want to set/modify a static IP address for Network Manager ( I'm using Red Hat Enterprise Linux 6.3 ), the relevant configuration file is: -
/etc/sysconfig/network-scripts/ifcfg-Auto_eth0
TYPE=Ethernet
BOOTPROTO=none
IPADDR=192.168.8.144
PREFIX=24
GATEWAY=192.168.8.2
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="Auto eth0"
UUID=78dd3baf-7fa9-4413-8174-ac44652a9371
ONBOOT=yes
HWADDR=00:0C:29:4B:80:A4
DNS1=192.168.8.2
LAST_CONNECT=1363700527
BOOTPROTO=none
IPADDR=192.168.8.144
PREFIX=24
GATEWAY=192.168.8.2
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="Auto eth0"
UUID=78dd3baf-7fa9-4413-8174-ac44652a9371
ONBOOT=yes
HWADDR=00:0C:29:4B:80:A4
DNS1=192.168.8.2
LAST_CONNECT=1363700527