DHCP server (basic) configuration in RHEL 6

Open the dhcp configuration file:

# vim /etc/dhcp/dhcpd.conf

// global section of the conf file:

option broadcast-address 192.168.1.255;       //broadcast address

option routers 192.168.1.1;                            // router address

option doamin-name "domain.com"              // domain name

default-lease-time 6000;                               

max-lease-time 72000;

subnet 192.168.1.0 netmask 255.255.255.0 {        // define subnet and netmask

range 192.168.1.10 192.168.1.20;                          // defining range

option domain-name-servers 192.168.1.127, 125.22.47.125;           // defining DNS IP

host system1 {                                                         // defining one host with any name

hardware ethernet 00:1C:23:4C:3B:25;                  // defining MAC address

fixed-address 192.168.1.12;                                   // defining fixed IP address for the host system

}

}

Note: The system having defined MAC address will always get the fixed IP address.

Since the “host block” is defined under “subnet” block-1, and the DNS IPs are defined under it,

the “host” will have access of the DNS system and the Internet as the DNS IPs are defined as globel in the block.

subnet 192.168.1.0 netmask 255.255.255.0 {            // new subnet block

range 192.168.1.21 192.168.1.30;                              // IP range

host system3 {                                                             // defining host

hardware ethernet a1:b2:c3:d4:e5:f3;                       // defining MAC address

fixed-address 192.168.1.22;                                       // defining IP address

}

}

Note: Because no DNS IP is defined in the “subnet” block-2, defined “host” under the block will not have access to the internet.

You can also define the host block in this way:

host system3 {                                                             // defining host

hardware ethernet a1:b2:c3:d4:e5:f3;                       // defining MAC address

fixed-address 192.168.1.22;                                       // defining IP address

option domain-name-servers 192.168.1.127, 125.22.47.125;           // because of the DNS entry                 //  in the “host” block, it will get access to the internet.

}

When dhcpd is running it will generate entries in the file: /var/lib/dhcp/dhcpd.leases:

lease 192.168.1.128 {

starts 2 2004/12/01 20:07:05;

ends 3 2004/12/02 08:07:05;

hardware ethernet 00:00:e8:4a:2c:5c;

uid 01:00:00:e8:4c:5d:31;

client-hostname "Node1";

}