How To Install DHCP Server In Linux

Apr 4, 2021

· 1 min read

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#### 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:

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Install Ubuntu and update the OS

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Install the ISC ( Internet Systems Consortium) DHCP service

sudo apt install isc-dhcp-server

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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"

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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;
}

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Start and check DHCP service

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

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DHCP Relay Agent

Configure a DHCP Relay Agent on Layer 3 gateways to point to the DHCP server

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Firewall Rules to allow DHCP traffic

Allow UDP traffic from the LAN subnet, source port 68, to the DHCP server, destination port 67

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Check leasing

sudo dhcp-lease-list

NOTE: This does not show reserved IPs. Check the config file for that

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