Q. I’ve HP Laptop installed with CentOS 5 workstation operating system. How can I configure Linux dhclient command to continuously requests an IP lease until one is granted by DHCP Server / Router?

A. You need to set the PERSISTENT_DHCLIENT option by editing Ethernet configuration file. This option is turned off by default.

Login as the root user

Open /etc/sysconfig/network-scripts/ifcfg-eth0 file to set eth0 to persistently look for an IP address lease:
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
Append line PERSISTENT_DHCLIENT=1, at the end configuration should look as follows:
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=dhcp
PERSISTENT_DHCLIENT=1

Save and close the file. Restart networking service or reboot laptop / desktop to test the changes:
# /etc/init.d/networking restart

Please note that your network switches and other protocol may need to configure properly to work with this option.