Step‑by‑Step Guide to Installing a DHCP Server on CentOS 6.5

Overview

DHCP (Dynamic Host Configuration Protocol) is commonly used in large LAN environments to centrally manage and assign IP addresses, gateway addresses, DNS server addresses, thereby improving address utilization.

Working Principle

DHCP operates through four broadcast phases: DISCOVER, OFFER, REQUEST, and ACK. A client without an IP broadcasts a DISCOVER message; any DHCP server can respond with an OFFER. The client selects an OFFER (usually the first received) and broadcasts a REQUEST to confirm the chosen server. The server finalizes the assignment with an ACK, delivering the IP, subnet mask, gateway, and DNS information. Renewal follows a similar broadcast process, with ACKs confirming continued use or NACKs triggering a new allocation cycle.

Allocation Methods

Automatic allocation: the assigned IP is used permanently.

Manual allocation: the DHCP administrator explicitly assigns a specific IP.

Dynamic allocation: the IP is released after use and can be reassigned to other clients.

Advantages

Reduces administrator workload.

Prevents IP address conflicts.

When the network changes its address range, individual client reconfiguration is unnecessary.

Improves IP address utilization.

Facilitates client configuration.

Address Information Distributed by DHCP

Client IP address and subnet mask.

Network address and broadcast address.

Default gateway address.

DNS server addresses.

Experimental Environment

Operating system: CentOS 6.5

Host IP address: 192.168.1.20

RPM package: dhcp-4.1.1-38.P1.el6.centos.x86_64.rpm

Setup Steps

(1) Install the DHCP service package on the server.

cd /mnt/sr0/Packages/

rpm -ivh dhcp-4.1.1-38.P1.el6.centos.x86_64.rpm

(2) View the main configuration file.

vim /etc/dhcp/dhcpd.conf

(3) Copy the sample configuration and edit it.

cp /usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample /etc/dhcp/dhcpd.conf

vim /etc/dhcp/dhcpd.conf

(4) Test the configuration on a client machine.

vim /etc/sysconfig/network-scripts/ifcfg-eth0

(5) Assign a static IP to a specific host.

First, obtain the client’s MAC address.

Then edit the server’s dhcpd.conf to add a host reservation.

vim /etc/dhcp/dhcpd.conf