Configure ISC-DHCP server

From Wikiversity
Jump to navigation Jump to search

In this article, we will describe the steps and procedures required to install and configure ISC-DHCP server on a Linux machine, (specifically Ubuntu 14.04).

Step 1
Installing ISC-DHCP server

To install ISC-DHCP server on Ubuntu 14.04, use the following commands Update Linux files

Update command will fetch the packages from its location and updates them to newer version.

    sudo apt-get update     

Installs ISC-DHCP Server

    sudo apt-get install isc-dhcp-server

Step 2
Configuring ISC-DHCP sever - dhcpd.conf

The ISC-DHCP server configuration file is dhcpd.conf and can be accessed using the following command

    sudo nano /etc/dhcp/dhcpd.conf

This command will allow to make changes in the dhcp configuration file "dhcpd.conf" which is at specified path.

We are required to do the following modifications in dhcpd.conf file:

    subnet netmask {
        option routers;
        option broadcast-address;
        default-lease-time 3600;
        max-lease-time 7200;
        option domain-name-servers;
        option domain-name "";

The following command is used to make the DHCP server an authoritative server for local network.


The following command is used to check the syntax of dhcpd.conf file for errors

     dhcpd -t

The following command will allow to edit the isc-dhcp-server file, where we can manually determine the interface of the server.

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

We have to set the interfaces to wlan0 in our file

     INTERFACES= "wlan0"

The following line will display the contents of the current routing tables.

     ip route

Step 3
Securing DHCP server The following modifications are done to configuration file to secure the DHCP server

     ddns-update-style none;
     deny declines;
     deny bootp;

The DoS attack on DHCP server can be avoided by denying the DHCP decline messages and can deny supporting old bootp clients.

Step 4
Restart ISC-DHCP server

Now that the isc-dhcp-server configuration is complete, we need to reload the dhcp server, so that the new configurations can be implemented

    sudo service isc-dhcp-server restart
    sudo service isc-dhcp-server start
    sudo service isc-dhcp-server stop

Step 5
Verifying.. Inorder to check the leases of the IP addresses assigned by the DHCP

     cd /var/lib/dhcp/
     ls -l
     cat dhcpd.leases