(install-isc-dhcp-server)=
# How to install and configure isc-dhcp-server

> **Note**:
> Although Ubuntu still supports `isc-dhcp-server`, this software is [no longer supported by its vendor](https://www.isc.org/blogs/isc-dhcp-eol/). It has been replaced by [Kea](https://www.isc.org/kea/).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, {ref}`refer to this guide instead <install-isc-kea>`.

## Install isc-dhcp-server

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

```bash
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:

```text
# 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
```

## Further reading

- The [isc-dhcp-server Ubuntu Wiki](https://help.ubuntu.com/community/isc-dhcp-server) page has more information.

- For more `/etc/dhcp/dhcpd.conf` options see the [dhcpd.conf man page](https://manpages.ubuntu.com/manpages/focal/en/man5/dhcpd.conf.5.html).

- [ISC dhcp-server](https://www.isc.org/software/dhcp)