How to install and configure isc-dhcp-server

Note:
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Although Ubuntu still supports isc-dhcp-server, this software is no longer supported by its vendor. It has been replaced by Kea.

In this guide we show how to install and configure isc-dhcp-server, which installs the dynamic host configuration protocol daemon, dhcpd. For isc-kea instructions, refer to this guide instead.

Install isc-dhcp-server

At a terminal prompt, enter the following command to install isc-dhcp-server:

sudo apt install isc-dhcp-server

Note:
You can find diagnostic messages from dhcpd in syslog.

Configure isc-dhcp-server

You will probably need to change the default configuration by editing /etc/dhcp/dhcpd.conf to suit your needs and particular configuration.

Most commonly, what you want to do is assign an IP address randomly. This can be done with /etc/dhcp/dhcpd.conf settings as follows:

# minimal sample /etc/dhcp/dhcpd.conf
default-lease-time 600;
max-lease-time 7200;
    
subnet 192.168.1.0 netmask 255.255.255.0 {
 range 192.168.1.150 192.168.1.200;
 option routers 192.168.1.254;
 option domain-name-servers 192.168.1.1, 192.168.1.2;
 option domain-name "mydomain.example";
}

This will result in the DHCP server giving clients an IP address from the range 192.168.1.150 - 192.168.1.200. It will lease an IP address for 600 seconds if the client doesn’t ask for a specific time frame. Otherwise the maximum (allowed) lease will be 7200 seconds. The server will also “advise” the client to use 192.168.1.254 as the default-gateway and 192.168.1.1 and 192.168.1.2 as its DNS servers.

You also may need to edit /etc/default/isc-dhcp-server to specify the interfaces dhcpd should listen to.

INTERFACESv4="eth4"

After changing the config files you need to restart the dhcpd service:

sudo systemctl restart isc-dhcp-server.service