configure a DHCP server in Ubuntu

sudo apt-get install isc-dhcp-server

sudo vim /etc/default/isc-dhcp-server

get the following:

#Defaults for dhcp initscript
#sourced by /etc/init.d/dhcp
#installed at /etc/default/isc-dhcp-server by the maintainer scripts
#
#This is a POSIX shell fragment
#
#On what interfaces should the DHCP server (dhcpd) serve DHCP requests"
#Separate multiple interfaces with spaces, e.g. “eth0 eth1".
INTERFACES="eth0"

Replace eth0 above with the name of your network interface that you want the server to lease addresses on.

sudo vim /etc/dhcp/dhcpd.conf

give you the output below.

#Sample configuration file for ISC dhcpd for Debian
#
#Attention: If /etc/ltsp/dhcpd.conf exists, that will be used as
#configuration file instead of this file.
#
#
....
option domain-name “example.org”;
option domain-name-servers ns1.example.org, ns2.example.org;
default-lease-time 600;
max-lease-time 7200;
log-facility local7;
subnet 10.0.0.0 netmask 255.255.255.0 {
range 10.0.0.150 10.0.0.253;
option routers 10.0.0.2;
option subnet-mask 255.255.255.0;
option broadcast-address 10.0.0.254;
option domain-name-servers 10.0.0.1, 10.0.0.2;
option ntp-servers 10.0.0.1;
option netbios-name-servers 10.0.0.1;
option netbios-node-type 8;
 ......
}

Adjust your settings according to your network requirements.
Range should be the range of ip addresses that you want the server to give out to clients.

Now restart the dhcp service by typing:

sudo /etc/init.d/isc-dhcp-server restart
# or 
sudo service isc-dhcp-server restart

check:

sudo netstat -uap

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address State PID/Program name
udp        0      0 10.0.0.255:netbios-dgm  *:*                   1016/nmbd
udp        0      0 10.0.0.255:netbios-ns   *:*                   1016/nmbd
udp        0      0 *:bootps                *:*                   4525/dhcpd
udp        0      0 *:netbios-dgm           *:*                   1016/nmbd
udp        0      0 *:netbios-ns            *:*                   1016/nmbd
udp        0      0 chris-desktop:domain    *:*                   1273/named
udp        0      0 chris-desktop.lo:domain *:*                   1273/named
udp        0      0 chris-deskt:netbios-dgm *:*                   1016/nmbd
udp        0      0 chris-deskto:netbios-ns *:*                   1016/nmbd
udp6       0      0 [::]:domain             [::]:*                1273/named