System information

Introduction 25
DHCP on the OnBoard
DHCP Server
A DHCP server (dhcpd) is present but disabled on the OnBoard by default.
The OnBoard administrator may want to enable the DHCP server to provide
fixed IP addresses for connected devices that are running DHCP client
software. The fixed IP addresses use the following DHCP features:
• Persistent leases, which allow the device on the private side of the
OnBoard to keep the same IP address even after the OnBoard or the
device is powered down and up again.
• Persistent storage of lease information, with the leases file and the
dhcpd configuration files stored in the flash memory and available to be
optionally updated from time to time when dhcpd is enabled.
• Preconfigured leases: using the MAC address of the device, the OnBoard
administrator can assign an IP address to a client before the OnBoard sees
the device on the network.
Note: IP addresses assigned to connected devices must remain constant over
time because each device is assigned an IP address as part of its configuration
on the OnBoard. For that reason, the OnBoard DHCP server should not be
used to provide dynamic IP addresses to devices.
The ability of DHCP to supply fixed addresses can be used to implement the
addressing scheme for connected devices, which is described in the following
sections of this manual:
• “Preparing an Addressing Scheme” on page 48
• “Address Configuration for Connected Devices” on page 372).
The OnBoard administrator can enable the DHCP server and assign IP
addresses to devices by logging into the OnBoard command line as root and
manually editing the /etc/dhcpd.conf file and performing other steps
described under “Configuring the DHCP Server” on page 77.