Dhcp configuration file Example

Example Subnet Declaration

subnet 192.168.1.0 netmask 255.255.255.0 {

        option routers                  192.168.1.254;

        option subnet-mask              255.255.255.0;

        option domain-search              "example.com";

        option domain-name-servers       192.168.1.1;

        option time-offset              -18000;     # Eastern Standard Time

        range 192.168.1.10 192.168.1.100;

}

To configure a DHCP server that leases a dynamic IP address to a system within a subnet, modify “Range Parameter” with your values. It declares a default lease time, maximum lease time, and network configuration values for the clients. This example assigns IP addresses in the range192.168.1.10 and 192.168.1.100 to client systems.

Range Parameter

default-lease-time 600;

max-lease-time 7200;

option subnet-mask 255.255.255.0;

option broadcast-address 192.168.1.255;

option routers 192.168.1.254;

option domain-name-servers 192.168.1.1, 192.168.1.2;

option domain-search "example.com";

subnet 192.168.1.0 netmask 255.255.255.0 {

   range 192.168.1.10 192.168.1.100;

}

 To assign an IP address to a client based on the MAC address of the Network interface card, use the hardware ethernet parameter within a hostdeclaration. As demonstrated in "Static IP Address using DHCP", the host apex declaration specifies that the network interface card with the MAC address 00:A0:78:8E:9E:AA always receives the IP address 192.168.1.4.

Note that the optional parameter host-name can also be used to assign a host name to the client.

Static IP Address using DHCP

host apex {

   option host-name "apex.example.com";

   hardware ethernet 00:A0:78:8E:9E:AA;

   fixed-address 192.168.1.4;

}

All subnets that share the same physical network should be declared within a shared-network declaration as shown in "Shared-network Declaration". Parameters within the shared-network, but outside the enclosed subnet declarations, are considered to be global parameters. The name of the shared-network must be a descriptive title for the network, such as using the title 'test-lab' to describe all the subnets in a test lab environment.

Shared-network Declaration

shared-network name {

    option domain-search              "test.redhat.com";

    option domain-name-servers      ns1.redhat.com, ns2.redhat.com;

    option routers                  192.168.0.254;

    more parameters for EXAMPLE shared-network

    subnet 192.168.1.0 netmask 255.255.252.0 {

        parameters for subnet

        range 192.168.1.1 192.168.1.254;

    }

    subnet 192.168.2.0 netmask 255.255.252.0 {

        parameters for subnet

        range 192.168.2.1 192.168.2.254;

    }

}

As demonstrated in "Group Declaration", the group declaration is used to apply global parameters to a group of declarations. For example, shared networks, subnets, and hosts can be grouped.

Group Declaration

group {

   option routers                  192.168.1.254;

   option subnet-mask              255.255.255.0;

   option domain-search              "example.com";

   option domain-name-servers       192.168.1.1;

   option time-offset              -18000;     # Eastern Standard Time

   host apex {

      option host-name "apex.example.com";

      hardware ethernet 00:A0:78:8E:9E:AA;

      fixed-address 192.168.1.4;

   }

   host raleigh {

      option host-name "raleigh.example.com";

      hardware ethernet 00:A1:DD:74:C3:F2;

      fixed-address 192.168.1.6;

   }

}