ComTech: IT Support Stirling

How to set up a dhcp server on Ubuntu Server 12.04 LTS

Today I will show you how to install and configure a dhcp server on Ubuntu Server 12.04 LTS.

The first thing we need to do is install the packages we need.  Open up a terminal and type:

sudo apt-get install isc-dhcp-server

There are two main files /etc/default/isc-dhcp-server and /etc/dhcp/dhcpd.conf which we will need to configure so lets take the first.  Open up a terminal and using your favourite text editor type:

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

You should 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?.


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

Onto the next file. Open up a terminal and type:

sudo nano /etc/dhcp/dhcpd.conf

which should 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.

# The ddns-updates-style parameter controls whether or not the server will
# attempt to do a DNS update when a lease is confirmed. We default to the
# behavior of the version 2 packages (‘none’, since DHCP v2 didn’t
# have support for DDNS.)
ddns-update-style none;

# option definitions common to all supported networks…
option domain-name “”;
option domain-name-servers,;

option domain-name “”;
default-lease-time 600;
max-lease-time 7200;

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.

# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
log-facility local7;

# No service will be given on this subnet, but declaring it helps the
# DHCP server to understand the network topology.

#subnet netmask {

# This is a very basic subnet declaration.

subnet netmask {
option routers;
option subnet-mask;

option broadcast-address;
option domain-name-servers,;

option ntp-servers;
option netbios-name-servers;
option netbios-node-type 8;

# option routers,;


# This declaration allows BOOTP clients to get dynamic addresses,
# which we don’t really recommend.

#subnet netmask {
# range dynamic-bootp;
# option broadcast-address;
# option routers;

# A slightly different configuration for an internal subnet.
#subnet netmask {
# range;
# option domain-name-servers;
# option domain-name “”;
# option routers;
# option broadcast-address;
# default-lease-time 600;
# max-lease-time 7200;

# Hosts which require special configuration options can be listed in
# host statements. If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.

#host passacaglia {
# hardware ethernet 0:0:c0:5d:bd:95;
# filename “vmunix.passacaglia”;
# server-name “”;

# Fixed IP addresses can also be specified for hosts. These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP. Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.
#host fantasia {
# hardware ethernet 08:00:07:26:c0:a5;
# fixed-address;

# You can declare a class of clients and then do address allocation
# based on that. The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.

#class “foo” {
# match if substring (option vendor-class-identifier, 0, 4) = “SUNW”;

#shared-network 224-29 {
# subnet netmask {
# option routers;
# }
# subnet netmask {
# option routers;
# }
# pool {
# allow members of “foo”;
# range;
# }
# pool {
# deny members of “foo”;
# range;
# }


This needs a little bit of explaining.

1. Everything in bold needs adding to the file.  Adjust your settings according to your network requirements.

2. The option domain name is your dns zone name.  For example mine is set to

3. 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 service isc-dhcp-server restart

Thats it!! Your dhcp server should be running, however it is best to check.  Open up a terminal and type:

sudo netstat -uap

which will show you the following information:


Active Internet connections (servers and established)

Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name

udp 0 0 *:55827 *:* 916/avahi-daemon: r
udp 0 0 chris-desktop.lo:domain *:* 1273/named
udp 0 0 chris-desktop:domain *:* 1273/named
udp 0 0 *:bootps *:* 4525/dhcpd
udp 0 0 *:17500 *:* 1768/dropbox
udp 0 0 *:54407 *:* 4539/VirtualBox
udp 0 0 *:* 1016/nmbd
udp 0 0 chris-deskto:netbios-ns *:* 1016/nmbd
udp 0 0 *:netbios-ns *:* 1016/nmbd
udp 0 0 *:* 1016/nmbd
udp 0 0 chris-deskt:netbios-dgm *:* 1016/nmbd
udp 0 0 *:netbios-dgm *:* 1016/nmbd
udp 0 0 *:mdns *:* 916/avahi-daemon: r
udp6 0 0 [::]:domain [::]:* 1273/named
udp6 0 0 [::]:51853 [::]:* 916/avahi-daemon: r
udp6 0 0 [::]:mdns [::]:* 916/avahi-daemon: r


This shows that the dhcp daemon is working

About the Author


Hi I’m Chris Wakefield the owner of ComTech IT Support. I provide Windows, Mac and Linux based IT Support to small businesses in Stirling, Alloa and Falkirk.

Follow @Comtech247 on Twitter




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