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Dynamic Host Configuration Protocol (DHCP) Server

The Dynamic Host Configuration Protocol (DHCP) is used to configure the network-layer addressing. The dhcpd daemon used to be configured using both a configuration file (/etc/dhcp/dhcpd.conf) and a daemon options file that was distribution-dependent. Recent versions of dhcp have moved the daemon options into systemd.

The daemon options are configured in a separate file:

On CentOS​

/etc/sysconfig/dhcpd

On Ubuntu​

/etc/default/isc-dhcp-server

On OpenSUSE​

/etc/sysconfig/dhcpd

The dhcp server will only serve out addresses on an interface that it finds a subnet block defined in the /etc/dhcp/dhcpd.conf file. It is no longer a requirement to explicitly tell dhcp which interfaces to use.

Additional or different daemon command line options may be passed to the daemon at start time by the systems' drop-in files. Please see the COMMAND LINE section in the dhcpd man page for additional details.

Configuration​

Global options are settings which should apply to all the hosts in a network. You can also define options on a per-network basis.

A sample configuration would be:

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;
  }