National Instruments ENET-232 Series, Manual

Page: 83 / 237

Using DHCP
The Dynamic Host Configuration Protocol (DHCP) is designed for large
networks in which networking devices are transient and network
parameters cannot be statically assigned and thus tied to specific
devices. DHCP eases the addition of networking devices onto a network
by having a server assign necessary network parameters, including the
IP address, netmask, and router information, to a newly attached network
device. Optionally, if the device provides a hostname with the
configuration request, DHCP may attempt to configure your network to
recognize the device with the requested hostname.
DHCP requires a Domain Name Server (DNS) to associate the numerical
IP address assigned with the requested hostname. Within the past few
years, an Internet community standard has emerged to provide a
standardized way for these services to provide dynamic domain name
services. Using this standard, after DHCP assigns the numerical IP
address, it can communicate with DNS to register the newly assigned IP
address with the requested hostname. However, the complexity of DHCP
and dynamic name registration typically requires active management by
a corporate MIS department, or equivalent, because of several risks for
failure.
One possible failure can occur if the pool of available addresses contains
no more unassigned IP addresses. This problem is evident if DHCP fails
to work and the
PWR/RDY LED continues to flicker for longer than 90
seconds at power on. In this situation, you need to obtain a static IP
address from your network administrator and configure the device
yourself using the NI Ethernet Device Configuration utility. Notice that if
DHCP fails to assign you an address, the current subnet might not have
an address available for you to use. In this case, you may need to move
your product to another subnet where there is an available IP address.
Failure also happens if communication between DHCP and DNS does
not occur. In this situation, DHCP assigns an address to the device, but
you cannot communicate to it using the hostname you assigned. Your
network administrator may need to insert the hostname manually into the
DNS table. Alternately, you can use the NI Ethernet Device Configuration
utility to determine the hostname associated with your assigned IP
address, and change the hostname to match the DNS entry. Refer to
Verifying the Hostname for more information.