Install and Configure DHCP Server & Client on CentOS 8 / RHEL 8

Admin

This guide will walk you through the steps to install DHCP Server & DHCP Client on CentOS 8 / RHEL 8 Linux server. If your question is how do I Install and Configure DHCP Server on CentOS 8 / RHEL 8?, then this guide is for you. A DHCP Server deployed in your organization can really make your network management a breeze. You can put to rest the hurdles of manually assigning IP addresses on every machine in your organization, and let a DHCP Server do this task that can get quite boring and unnecessarily repetitive.

In this guide, we are going to install and configure a DHCP Server and Client in CentOS 8 / RHEL 8 machine. We’ll cover both the server side setup and all the client side configurations required. Let’s start the configuration of DHCP ( Dynamic Host Configuration Protocol ) Server to assign IP addresses to client hosts in our local network.

Step 1: Install DHCP Server on CentOS 8 / RHEL 8

Install DHCP server package using the dnf installer.

sudo dnf -y install dhcp-server

This will install any dependency required to run DHCP Server on CentOS 8 / RHEL 8.

Step 2: Configure DHCP Server on CentOS 8 / RHEL 8

Edit the DHCP server configuration file on CentOS 8 / RHEL 8.

sudo vi /etc/dhcp/dhcpd.conf

My configuration file will be populated with these parameters:

  • Domain name: example.com
  • DNS Server: ns1.example.com
  • DHCP network: 192.168.21.0
  • DHCP Subnet mask: 255.255.255.0
  • Range of IP addresses to allocate: 192.168.21.30 – 192.168.21.200
  • Default gateway: 192.168.21.1
  • DHCP Lease Time: 600
  • DHCP Maximum Lease Time: 7200

The DHCP server configuration file looks like this:

# Set DNS name and DNS server's IP address or hostname
option domain-name     "example.com";
option domain-name-servers     ns1.example.com;

# Declare DHCP Server
authoritative;

# The default DHCP lease time
default-lease-time 600;

# Set the maximum lease time
max-lease-time 7200;

# Set Network address, subnet mask and gateway

subnet 192.168.21.0 netmask 255.255.255.0 {
    # Range of IP addresses to allocate
    range dynamic-bootp 192.168.21.30 192.168.21.200;
    # Provide broadcast address
    option broadcast-address 192.168.21.255;
    # Set default gateway
    option routers 192.168.21.1;
}

Start and enable the dhcpd service after making the changes in the configuration file.

sudo systemctl enable --now dhcpd

If you have firewalld running, allow the service port to be accessible from your network.

sudo firewall-cmd --add-service=dhcp --permanent 
sudo firewall-cmd --reload

Step 3: Configure DHCP Client

Install DHCP client in your Linux machine to get an IP address automatically.

----------- CentOS 8 / RHEL 8 / Fedora -----------
$ sudo dnf -y install dhcp-client 

$ sudo yum -y install dhcp-client

Manually request for DHCP IP address

You can use dhclient command to request for an IP address manually.

$ sudo dhclient <interface>
E.g:
$ sudo dhclient eth0

# Confirm
$ ip ad
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 52:54:00:10:47:63 brd ff:ff:ff:ff:ff:ff
    inet 192.168.21.106/24 brd 192.168.21.255 scope global noprefixroute dynamic eth0
       valid_lft 3594sec preferred_lft 3594sec
    inet6 fe80::5054:ff:fe10:4763/64 scope link 
       valid_lft forever preferred_lft forever

Persist configurations – CentOS / RHEL / Fedora with systemd

  • Edit configurations with nmcli
ifname="eth0"
nmcli connection modify ${ifname} ipv4.method auto
nmcli connection down ${ifname}; nmcli connection up ${ifname}
  • Manually edit network configuration file
$ sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE="eth0"
BOOTPROTO="dhcp"
ONBOOT="yes"
TYPE="Ethernet"
PERSISTENT_DHCLIENT="yes"

Persist configurations – Debian

$ sudo nano /etc/network/interfaces
iface ens3 inet dhcp

$ sudo systemctl restart ifup@ens3

Persist configurations – Ubuntu

$ sudo nano /etc/netplan/01-netcfg.yaml
network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      dhcp4: yes

$ sudo netplan apply

Reserving IP address on DHCP Server

You can reserve an IP address for a computer or device in your network if you have its MAC address:

$ sudo vi /etc/dhcp/dhcpd.conf
# Add lines like below for each host
host myserver {
    hardware ethernet 00:50:56:8c:20:fd;
    fixed-address  192.168.21.100;
}