DHCPD Quick Setup Instructions

Sample of how to set up DHCPD server on Red Hat 7.0

1. Copy over the sample dhcpd.conf file

cp /usr/share/doc/dhcp-2.0pl5/dhcpd.conf.sample /etc/dhcpd.conf

2. Edit /etc/dhcpd.conf

Here’s a copy of the unmodified sample:

subnet 192.168.0.0 netmask 255.255.255.0 {
# --- default gateway
	option routers			192.168.0.1;
	option subnet-mask		255.255.255.0;

	option nis-domain		"domain.org";
	option domain-name		"domain.org";
	option domain-name-servers	192.168.1.1;

	option time-offset		-5;	# Eastern Standard Time
#	option ntp-servers		192.168.1.1;
#	option netbios-name-servers	192.168.1.1;
# --- Selects point-to-point node (default is hybrid). Don't change this unless
# -- you understand Netbios very well
#	option netbios-node-type 2;

	range dynamic-bootp 192.168.0.128 192.168.0.255;
	default-lease-time 21600;
	max-lease-time 43200;

	# we want the nameserver to appear at a fixed address
	host ns {
		next-server marvin.redhat.com;
		hardware ethernet 12:34:56:78:AB:CD;
		fixed-address 207.175.42.254;
	}
}

Here’s the file I used after modifying the above sample:

subnet 192.168.0.0 netmask 255.255.255.0 {
# --- default gateway
	option routers			192.168.0.1;
	option subnet-mask		255.255.255.0;

	option nis-domain		"linuxclinic.org";
	option domain-name		"linuxclinic.org";
	option domain-name-servers	192.168.0.100;

	option time-offset		-6;	# Central Standard Time
#	option ntp-servers		192.168.1.1;
#	option netbios-name-servers	192.168.1.1;
# --- Selects point-to-point node (default is hybrid). Don't change this unless
# -- you understand Netbios very well
#	option netbios-node-type 2;

#Dhcpd server will give out addresses between 128 and 255
	range dynamic-bootp 192.168.0.128 192.168.0.255;
	default-lease-time 21600;
	max-lease-time 43200;

#server.linuxclinic.org:/techtour/ks.cfg is the nfs share
#     for a kickstart confgiuration file
	filename "/techtour/ks.cfg";
	next-server server.linuxclinic.org;
}

#I'm handing out fixed addresses and names for the following mac addresses
#Cim Console
host TechCommEv {
	hardware ethernet 00:80:5f:1d:57:47;
	fixed-address 192.168.0.2;
}
host tech1 {
	hardware ethernet 00:50:8b:d3:f9:ed;
	fixed-address 192.168.0.30;
	option host-name "tech1";
}
host tech2 {
	hardware ethernet 00:50:8b:e1:5d:dc;
	fixed-address 192.168.0.31;
	option host-name "tech2";
}
host tech3 {
	hardware ethernet 00:50:8b:e1:e8:f2;
	fixed-address 192.168.0.32;
	option host-name "tech3";
}
host tech4 {
	hardware ethernet 00:50:8b:e0:1c:e2;
	fixed-address 192.168.0.33;
	option host-name "tech4";
}
host tech5 {
	fixed-address 192.168.0.34;
	option host-name "tech5";
	hardware ethernet 00:50:8b:f2:c5:c4;
}

3. If your dhcpd.leases file doesn’t exist, then generate it with the touch command

touch /var/lib/dhcp/dhcpd.leases

4. Restart dhcpd

/etc/rc.d/init.d/dhcpd restart

5. Check that dhcpd is running

ps ax | grep dhcpd | grep -v grep

6. If dhcpd is not running, then run it directly to get more description on the error

/usr/sbin/dhcpd

7. Also check /var/log/messages for other error messages

tail -50 /var/log/messages

8. Make sure that you have dhcpd starting on bootup

chkconfig --list dhcpd

9. If it is not set for runlevels 2345, then set it

chkconfig --level 2345 dhcpd on

10. After adding my 2nd network card, I noticed dhcpd wasn’t working anymore.

    If more than one network card resides in the DHCP server, it is recommended to specify which interface(s) the DHCP server will use. Edit /etc/sysconfig/dhcpd by adding the appropriate interface to the DHCPDARGS= line. The entry in /etc/sysconfig/dhcpd should appear as follows:

    DHCPDARGS=eth0

    The dhcpd server loads without problem after adding this entry.

11. Check out the pump.html page if you will be working with Linux dhcp clients. Pump can be used to request, release, or give status on dhcp responses.
12. Cool test

ping -c 2 -b 192.138.0.255 | sort
arp -a

13. More Info / Debugging

Here are several means for debugging in no particular order:

• /usr/sbin/dhcpd -d -f
• tail -f /var/lib/dhcpd.leases
• tail -f /var/log/messages
14. Getting Help

You can look at the help files: “man dhcpd” and “man dhcpd.conf”.