You could manually and termporarily get an dynamic ip address from dhcp server like this:
dhclient eth0; # renew dhcp lease, ask for dhcp address, where eth0 is probably the nic you want
The /etc/sysconfig/network file should contain the following line:
The NETWORKING variable must be set to yes if you want networking to start at boot time.
The /etc/sysconfig/network-scripts/ifcfg-eth0 file should contain the following lines:
DEVICE=eth0 BOOTPROTO=dhcp ONBOOT=yes
A configuration file is needed for each device to be configured to use DHCP.