How To Install DHCP Server In Linux

Apr 4, 2021 · 1 min read

In the video below, we show you how to install DHCP server in Linux using Ubuntu 20.04 LTS and ISC DHCP server

We’ll also set up a DHCP Relay Agent and firewall rules to service DHCP requests in a different subnet

Useful links:
https://ubuntu.com/download/server

Installation and configuration example:

Install Ubuntu and update the OS
Install the ISC ( Internet Systems Consortium) DHCP service
```
sudo apt install isc-dhcp-server
```

Bind DHCP to a specific interface

cd /etc/default  
sudo cp isc-dhcp-server isc-dhcp-server.bak

Check the interface name

ip addr

Edit the config file

sudo nano isc-dhcp-server

INTERFACESv4="ens192"
INTERFACESv6="ens192"

Configure the DHCP service

cd /etc/dhcp
sudo cp dhcpd.conf dhcpd.conf.bak
sudo nano dhcpd.conf

# Global settings
option domain-name "templab.lan";
option domain-name-servers 172.16.17.10;

default-lease-time 600;
max-lease-time 7200;

# Disable DDNS
ddns-update-style none;

# Server is the authoritative DHCP server i.e. the only one
authoritative;

# Local subnet for network topology
subnet 172.16.17.0 netmask 255.255.255.0 {
}

# Pool to lease IP addresses from
subnet 172.16.19.0 netmask 255.255.255.0 {
 range 172.16.19.100 172.16.19.250;
 option routers 172.16.19.254;
}

# Reserved IP address for a specific host
host PC2 {
 hardware ethernet 00:0c:29:a9:d1:4c;
 fixed-address 172.16.19.40;
}

Start and check DHCP service

sudo systemctl start isc-dhcp-server
sudo systemctl status isc-dhcp-server

DHCP Relay Agent
Configure a DHCP Relay Agent on Layer 3 gateways to point to the DHCP server
Firewall Rules to allow DHCP traffic
Allow UDP traffic from the LAN subnet, source port 68, to the DHCP server, destination port 67
Check leasing
```
sudo dhcp-lease-list
```
NOTE: This does not show reserved IPs. Check the config file for that