Set a static internal IP

1. find a hooked interface

2. make a script in /etc/sysconfig/network-scripts
For example:
$cd /etc/sysconfig/network-scripts
$touch ifcfg-em1
$vim ifcfg-em1

DEVICE=em1

HWADDR=A4:BA:DB:1A:AC:4F this is the mac address of the interface

TYPE=Ethernet

ONBOOT=yes

NM_CONTROLLED=no

BOOTPROTO=static

IPADDR=192.168.0.27 this is the static IP you want to set

BROADCAST=192.168.0.255

NETMASK=255.255.255.0

NAME=em1

3. restart the device

$ ifdown em1

$ ifup em1

4. finally, check if the static ip has been assigned to interface em1

$ ifconfig