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9.1.4 Reboot
reboot time;
When the client is restarted, it first tries to reacquire the last address it had. This is called the
INIT-REBOOT
state. If it is still attached to the same network it was attached to when it last ran, this is the
quickest way to get started. The
reboot
statement sets the time that must elapse after the client first tries
to reacquire its old address before it gives up and tries to discover a new address. By default, the reboot
timeout is ten seconds.
9.1.5 Backoff-cutoff
backoff-cutoff
tim
e;
The client uses an exponential backoff algorithm with some randomness, so that if many clients try to
configure themselves at the same time, they will not make their requests in lockstep.
The
backoff-cutoff
statement determines the maximum amount of time that the client is allowed to back
off. The backoff-cutoff time defaults to two minutes.
9.1.6 Initial-interval
initial-interval
tim
e;
The
initial-interval
statement sets the amount of time between the first attempt to reach a server and the
second attempt to reach a server. Each time a message is sent, the interval between messages is
incremented by twice the current interval multiplied by a random number between zero and one. If it is
greater than the backoff-cutoff amount, it is set to that amount. The initial interval time defaults to ten
seconds.
9.2 Lease requirements and requests
The DHCP protocol allows the client to request that the server send it specific information, and not send
it other information that it is not prepared to accept. The protocol also allows the client to reject offers
from servers if they do not contain information the client needs, or if the information provided is not
satisfactory.
There is a variety of data contained in offers that DHCP servers send to DHCP clients. The data that can
be specifically requested are called
DHCP Option
s. DHCP Options are defined in [3], although an DHCP
client only supports a limited subset of those described there
9.2.1 Request
request [
option
] [, ...
optio
n];
The
request
statement causes the client to request that any server responding to the client send the client
its values for the specified options. Only the option names should be specified in the request statement -
not option parameters.
9.2.2 Require
require [
option
] [, ...
option
];
The
require
statement lists options that must be sent in order for an offer to be accepted. Offers that do
not contain
all
the listed options will be ignored.
9.2.3 Send
send { [
option declaration
] [ ...
option declaration
] }
The send statement causes the client to send the specified options to the server with the specified values.
Options that are always sent in the DHCP protocol should not be specified here, except that the client
can specify a
requested-lease-time
option other than the default requested lease time, which is two hours
(this would normally be done on a per-interface basis: see section 6.3.2). The other obvious use for this
statement is to send information to the server that will allow it to differentiate between this client and
other clients or kinds of clients.
