File konfigurasi DHCP /etc/dhcp/dhcpd.conf dijelaskan

File konfigurasi DHCP utama adalah /etc/dhcp/dhcpd.conf . File tersebut digunakan untuk menyimpan informasi konfigurasi jaringan yang diperlukan oleh klien DHCP. Ada juga contoh file konfigurasi di /usr/share/doc/dhcp-[version]/dhcpd.conf.sample .

# cat /usr/share/doc/dhcp*/dhcpd.conf.sample
# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

# option definitions common to all supported networks...
option domain-name "example.org";
option domain-name-servers ns1.example.org, ns2.example.org;

default-lease-time 600;
max-lease-time 7200;

# Use this to enble / disable dynamic dns updates globally.
#ddns-update-style none;

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
#authoritative;

# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
log-facility local7;

# No service will be given on this subnet, but declaring it helps the
# DHCP server to understand the network topology.

subnet 10.152.187.0 netmask 255.255.255.0 {
}

# This is a very basic subnet declaration.

subnet 10.254.239.0 netmask 255.255.255.224 {
  range 10.254.239.10 10.254.239.20;
  option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
}

# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.

subnet 10.254.239.32 netmask 255.255.255.224 {
  range dynamic-bootp 10.254.239.40 10.254.239.60;
  option broadcast-address 10.254.239.31;
  option routers rtr-239-32-1.example.org;
}

# A slightly different configuration for an internal subnet.
subnet 10.5.5.0 netmask 255.255.255.224 {
  range 10.5.5.26 10.5.5.30;
  option domain-name-servers ns1.internal.example.org;
  option domain-name "internal.example.org";
  option routers 10.5.5.1;
  option broadcast-address 10.5.5.31;
  default-lease-time 600;
  max-lease-time 7200;
}

# Hosts which require special configuration options can be listed in
# host statements.   If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.

host passacaglia {
  hardware ethernet 0:0:c0:5d:bd:95;
  filename "vmunix.passacaglia";
  server-name "toccata.fugue.com";
}

# Fixed IP addresses can also be specified for hosts.   These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP.   Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.
host fantasia {
  hardware ethernet 08:00:07:26:c0:a5;
  fixed-address fantasia.fugue.com;
}

# You can declare a class of clients and then do address allocation
# based on that.   The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.

class "foo" {
  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
}

shared-network 224-29 {
  subnet 10.17.224.0 netmask 255.255.255.0 {
    option routers rtr-224.example.org;
  }
  subnet 10.0.29.0 netmask 255.255.255.0 {
    option routers rtr-29.example.org;
  }
  pool {
    allow members of "foo";
    range 10.17.224.10 10.17.224.250;
  }
  pool {
    deny members of "foo";
    range 10.0.29.10 10.0.29.230;
  }
}

Parameter konfigurasi

1. opsi

Informasi adalah jalur opsi yang dikirim ke setiap klien saat meminta sewa. Misalnya, dalam contoh file konfigurasi di atas, subnet-mask, broadcast-address, alamat IP server DNS dan nama domain dikirim ke setiap klien. Setiap deklarasi opsi diakhiri dengan titik koma (;).

2. Waktu sewa

Ada entri terkait waktu dalam file konfigurasi.

• waktu-sewa-default :jumlah detik sewa tetap berlaku jika klien yang meminta sewa tidak menentukan durasinya.
• waktu sewa maksimum :Jumlah detik maksimum yang diperbolehkan untuk sewa.

3. deklarasi subnet

Deklarasi subnet mencakup rentang alamat IP yang dapat diberikan oleh server DHCP ke klien. Anda dapat menentukan beberapa subnet di sini. Subnet bisa dideklarasikan dalam kurung kurawal ({}) dan kita juga bisa menetapkan parameter lain ke subnet yang ditetapkan. Parameter yang ditentukan di luar kurung kurawal berlaku secara global untuk semua klien.

Deklarasi server DHCP tambahan

1. deklarasi host untuk penetapan alamat IP statis
Untuk memberikan alamat IP statis ke server klien tertentu, gunakan host deklarasi dan sertakan alamat MAC klien dan alamat IP statis yang akan ditetapkan ke host tersebut. Misalnya :

host server01 {
	hardware ethernet    00:14:3G:00:12:01;
	fixed-address        192.168.1.101;
	max-lease-time       84600; 
}

2. Deklarasi jaringan bersama
– Deklarasikan semua subnet yang berbagi jaringan fisik yang sama dalam jaringan bersama deklarasi.
– Parameter dalam jaringan bersama, tetapi di luar deklarasi subnet terlampir, dianggap sebagai parameter global. Misalnya (di sini parameter router berlaku untuk kedua subnet):

shared-network [name] {
	option routers 192.168.0.254
	subnet 192.168.1.0 netmast 255.255.252.0 {
		range 192.168.1.200 192.168.1.254;
	}
	subnet 192.168.2.0 netmast 255.255.252.0 {
		range 192.168.2.200 192.168.2.254;
	}
}

3. Deklarasi Grup
Gunakan grup deklarasi untuk menerapkan parameter global ke sekelompok deklarasi. Jaringan bersama, subnet, dan host dapat dikelompokkan bersama. Misalnya :

group {
	option routers 192.168.1.254;
	host server01 {
		hardware ethernet    00:14:3G:00:12:01;
		fixed-address        192.168.1.101;
	}
	subnet 192.168.1.0 netmast 255.255.252.0 {
		range 192.168.1.200 192.168.1.254;
	}
}