Technical data

Configuring the DHCP Client
8.2 DHCP Client Components
Table 8–1 (Cont.) Configuration Keywords
Keyword Description
start_delay seconds Specifies the maximum time (in seconds) the client
delays before broadcasting DHCP packets. When the
DHCP client is invoked to configure an interface it
will delay for a short time before broadcasting the
first DHCP packet. The delay time is randomized
from a value of 0 up to the value specified by seconds.
The TCP/IP commands SET INTERFACE/DHCP
and the START COMMUNICATION/INITIALZE
command (executed at product startup time) both
execute
dhcpconf start commands and experience the
randomized delay. The default value for seconds is 10
seconds.
timeouts
value,value,value....
Specifies how long the client should wait for replies
before timing out and retrying the broadcast.
The DHCP protocol requires clients to implement
an exponential retransmission and backoff when
broadcasting discover or request packets.
Each time the client sends a DHCP protocol packet,
it waits for a response until a timeout occurs after an
interval (in seconds) given by a member of the list of
values. If a timeout occurs, the packet retransmits
with the same XID (see RFC 1541), and the timeout is
set to the next positive value in the comma-separated
list. The last element in the list is negative or 0 (zero).
At this point, the next action depends on options to
the
DHCPCONF program. One option is to fail. Another
option is to retry forever. If the last value in the
list is negative, DHCP suspends configuration of the
interface for an amount of time given by the negative
number terminating the list of values. During this
time, the interface is considered idle—the client is not
expecting responses destined for the interface and will
ignore any that arrive. When the idle time is over,
the client begins retransmitting with a new XID, and
a timeout value is given by the first element in the
array of values. If the last value is 0 (zero), the client
continues to use the same XID and timeout of the last
positive value in the list of values. The default list of
values is 4, 8, 16, 32, 0.
use_saved_config Specifies to use the configuration stored in
ifname.DHC from a previous invocation of the protocol
if the following conditions exist:
• The lease is still valid.
• There is no reply to DHCP.
•
use_saved_config is set.
(continued on next page)
Configuring the DHCP Client 8–7