dhcp on linux

example: Build a dhcp server for general use.
Software: Redhat Linux 7.2 with all known patches distributed via Redhat update agent up to 12.21.01.
Hardware: PIII 450, 128mem, 8gig HD, CD, Floppy, 3com 3c905b-tx nic, and windows pcs set to get ip addresses from dhcp networked via hub/switch.

prior experience required: Need to be capable of Installing Redhat Linux. Must be able to log in as root. Either need direct access to server or a secure shell client and a PC. Need basic skills to navigate the filesystem via terminal. Also need to be able edit a text file.

installation: Either go to Redhat 7.2 cd#XXXX and install the file "dhcp-2.0pl5-8.i386.rpm", or find a redhat mirror near you and download the rpm installer file. The file name is "dhcp-XXX.i386.rpm". Either on cd or via ftp, the rpm installer files for Redhat are stored in "Redhat/RPMS". Log on in a terminal as root. Go to the directory that contains "dhcp-XXX.i386.rpm". Install the rpm file "# rpm -Uvh dhcp-XXX.i386.rpm". That is all for installation. This only installs the program files and documentation.

configuration: Now you need to create the configuration file for your dhcp server and the file that stores dhcp lease information. The documentation for dhcp is in "/usr/share/doc/dhcp-XXX/". Go there, look open read.... To create the configuration file copy and rename "dhcpd.conf.sample" as "/etc/dhcpd.conf" "# cp dhcpd.conf.sample /etc/dhcpd.conf". Now edit the file and input the settings specific to your subnet and dhcp range. Example files: clean sample file, edited sample file. Now create the lease info file. "# touch /var/lib/dhcp/dhcp.leases". Now you are ready to test your dhcp server.

test: To launch the dhcp server "# /etc/init.d/dhcpd start" other commands are "stop, restart, condrestart, status". If you recieved no error while starting dhcp good, go test. If you have an error in your configuration you will get a message notifying you of what line has an error on it, so you can edit and retest.
In my example I am using windows workstations as dhcp clients. ether start or restart the client machines or renew the clients ip address.

troubleshooting: Did the client get a dhcp address? If not verify the clients settings and reboot or renew and make sure you are allowing dhcp through any firewall that you may have. If you are using the firewall built into redhat, "# lokkit" will bring up a very basic firewall configuration tool that will allow you to open up the port for dhcp "click on the custom link to see".

tweaks: You can also create reservations for dhcp managed static addresses. Send atomic clock syncronization to the clients, use the dhcp server as the browse master for windows file sharing networks. see examples

automatic operation: To get dhcpd to start on from at boot/reboot you need to create a startup script in /etc/init.d/name and link it to /etc/rc3.d/#name

logging: a log file is kept in "/var/lib/dhcp/dhcp.leases". I would check out "# man dhcp.leases". It will explain how the logging works. One area that I need more research on before explaining, is logging clients that have reserved addresses. I will add that after further research.

reference: dhcp mini how to, man pages: dhclient(8), dhcrelay(8), dhcpd.conf(5), dhcpd.leases(5), dhcp-options(5)