dhcpclient(1M)dhcpclient(1M)NAMEdhcpclient - Client for Dynamic Host Configuration Protocol Server
hostname] tracefile] class-id] debug_level] server_ipaddress] log_type]
hostname] tracefile] debug_level] interface server_ipaddress] log_type]
tracefile] debug_level] interface server_ipaddress] log_type]
is used to obtain the configuration parameters from the Dynamic Host
Configuration Protocol server (bootpd(1M)) to configure the host. Cur‐
rently, supports 10bt (10BaseT) and 100bt (100BaseT) networks only. It
does not support networks.
is invoked by the script (see auto_parms(1M)) at boot up. The file is
used for the configuration of the interfaces. To invoke using the
script, set the variable to a non-zero value in the file. can also be
invoked at the command prompt, when the interface is not configured.
Once the obtains the configuration parameters from the server, it is
stored in a configuration file named The configuration parameters are
valid for a fixed time, lease time.
The configuration information in file will be of the following format.
The length field denotes the length of the data field following it.
All these lines collectively indicate one record. The configuration
file will have series of records.
Since this file contains all the configuration information, it can be
used to identify the server from which the configuration parameters
were obtained. The configuration file can also be used to obtain the
same configuration parameters from the server. So, once the is invoked,
it will try to read the configuration file,
While trying to read the file, the following conditions are possible:
1. It may be possible that the configuration file had been deleted or
it may not be available for reading.
2. The file may have got corrupted and contains irrelevant data for
the particular interface.
3. There may be no configuration information for the particular inter‐
4. User may have specified option meaning that a new lease is needed.
For all of the above cases, has to first find the server which is ready
for the service. For this purpose, it will send a message. If the user
has specified server_ipaddress using the option, then replies only from
the specified server will be accepted. The server in turn will reply
with the configuration parameters that it can offer. This message is
called If the client has sent the to broadcast address, then it will
receive from more than one server. The selects one of the obtained.
Then, it will send to the server, requesting the configuration parame‐
ters. The server will reply with a positive acknowledgement called if
it is willing to send the configuration parameters to the host and with
a negative acknowledgement, if it is not willing to do so. If the has
received it will copy all the configuration parameters to the configu‐
ration file, else, it will send another message and repeat the whole
process. This process is called "Obtaining a new lease".
If all the above 4 cases are not true, then the can directly send the
message and obtain the configuration parameters as mentioned above.
This process is called "Renewing the lease".
The various options supported by are as described below.
When this option is used, the client will accept the reply from the
server only if the in the request and reply packet
This option is used to send a hostname. The
hostname should be specified as an ASCII string.
This option is used during bootup time to obtain a new lease.
If the client is trying to obtain the configuration param‐
eters from the server for the first time, then does not
exist. So, using this option, the client obtains a new
lease for the interface specified.
This option is used for dumping the internal data of an
interface. A sample dump is shown below.
This option is used to specify the file name for the
This option is used for specifying the
of the device group. should be specified as an ASCII
This option is used for logging of debug information.
debug_level specifies the amount of debug information
logged. The debugging messages are sent to
This option is used for maintaining the lease. When invoked with this
the runs as a daemon. The calculates how much time it
needs to sleep before the lease needs to be renewed and
then sleeps for that time. When it wakes up, it extends
the lease by sending the request to the server.
This option is used for ignoring the current lease.
When this option is used, the current configuration infor‐
mation is discarded and request for a new lease is sent.
This option is used for tracing the packets. It
displays the packet contents in a readable format.
This option is used for releasing a lease. The
releases all the assigned configuration parameters. This
is done by sending the message to the server. The dhcp‐
client then empties the record corresponding to that
interface in the configuration file,
This option is used to specify the ip address of the
server from which the reply should be accepted.
server_ipaddress must be a unicast IP address specified in
dotted decimal form.
If the log_type is a non zero value and if the debug_level is low
enough for the process to detach from the tty (see sys‐
log(3C)), then, the logging goes to else it goes to This
option is used when the is running as a daemon.
This option prints the various version strings of the
This option is used to specify the number of attempts the
packet should be sent before obtaining a reply.
send_attempts must be specified as an unsigned number.
This option is used to specify the time interval between successive
retransmission. time_to_wait will be in seconds.
To the lease for the interface lan0 and invoke logging in the following
set of commands is invoked at the command prompt:
To trace the packet and get the debugging messages, use:
This is an example of a file.
00 4 lan0
01 5 dhcph
06 4 4294967295
07 4 4294967295
08 4 0
09 4 0
10 4 1
11 6 8 0 9 25 a5 b1
12 4 220.127.116.11
13 4 255.255.255.0
14 4 0.0.0.0
16 4 18.104.22.168
17 4 22.214.171.124
21 4 0.0.0.0
24 39 63 82 53 63 35 1 5 33 4 ff ff ff ff 36 4 c0 b8
16 3 1 4 ff ff ff 0 c 5 64 68 63 70 68 2 4 ff ff b2 a8 ff
was developed by HP.
SEE ALSOauto_parms(1M), bootpd(1M), bootpquery(1M), dhcptools(1M), syslog(3C).
DARPA Internet Request For Comments: RFC1541, RFC1542, RFC1533,
RFC1534, Assigned Numbers RFC.