dhcpclient(1M) dhcpclient(1M)
NAME
dhcpclient - Client for Dynamic Host Configuration Protocol Server
SYNOPSIS
hostname] tracefile] class-id] debug_level] server_ipaddress] log_type] send_attempts] time_to_wait]
interface server_ipaddress]
hostname] tracefile] debug_level] interface server_ipaddress] log_type] time_to_wait]
tracefile] debug_level] interface server_ipaddress] log_type]
DESCRIPTION
is used to obtain the configuration parameters from the Dynamic Host Configuration Protocol server (bootpd(1M)) to configure the host.
Currently, 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 interface.
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 configu-
ration parameters. 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 parame-
ters to the configuration 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.
Options
When this option is used, the client will accept the reply from the
server only if the in the request and reply packet matches.
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 parameters 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
debugging output.
This option is used for specifying the
of the device group. should be specified as an ASCII string.
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 option,
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 information 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 dhcpclient 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 syslog(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
to stdout.
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 packet
retransmission. time_to_wait will be in seconds.
EXAMPLES
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
02 0
03 0
04 0
05 0
06 4 4294967295
07 4 4294967295
08 4 0
09 4 0
10 4 1
11 6 8 0 9 25 a5 b1
12 4 192.11.22.107
13 4 255.255.255.0
14 4 0.0.0.0
15 0
16 4 192.11.22.3
17 4 192.11.22.3
18 0
19 0
20 0
21 4 0.0.0.0
22 0
23 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
AUTHOR
was developed by HP.
FILES
configuration file.
SEE ALSO
auto_parms(1M), bootpd(1M), bootpquery(1M), dhcptools(1M), syslog(3C).
DARPA Internet Request For Comments: RFC1541, RFC1542, RFC1533, RFC1534, Assigned Numbers RFC.
dhcpclient(1M)