dhclient - Remove wrong processing of option 33 (static routes).
[dragonfly.git] / sbin / dhclient / dhclient.conf.5
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ee1dc8e7 1.\" $OpenBSD: src/sbin/dhclient/dhclient.conf.5,v 1.21 2011/04/09 19:53:00 krw Exp $
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2.\"
3.\" Copyright (c) 1997 The Internet Software Consortium.
4.\" All rights reserved.
5.\"
6.\" Redistribution and use in source and binary forms, with or without
7.\" modification, are permitted provided that the following conditions
8.\" are met:
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10.\" 1. Redistributions of source code must retain the above copyright
11.\" notice, this list of conditions and the following disclaimer.
12.\" 2. Redistributions in binary form must reproduce the above copyright
13.\" notice, this list of conditions and the following disclaimer in the
14.\" documentation and/or other materials provided with the distribution.
15.\" 3. Neither the name of The Internet Software Consortium nor the names
16.\" of its contributors may be used to endorse or promote products derived
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18.\"
19.\" THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
20.\" CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
21.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
22.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
23.\" DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
24.\" CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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30.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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32.\"
33.\" This software has been written for the Internet Software Consortium
34.\" by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
35.\" Enterprises. To learn more about the Internet Software Consortium,
36.\" see ``http://www.isc.org/isc''. To learn more about Vixie
37.\" Enterprises, see ``http://www.vix.com''.
38.\"
ee1dc8e7 39.Dd August 4, 2012
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40.Dt DHCLIENT.CONF 5
41.Os
42.Sh NAME
43.Nm dhclient.conf
44.Nd DHCP client configuration file
45.Sh DESCRIPTION
46The
47.Nm
48file contains configuration information for
49.Xr dhclient 8 ,
50the Internet Software Consortium DHCP Client.
51.Pp
52The
53.Nm
54file is a free-form ASCII text file.
55It is parsed by the recursive-descent parser built into
56.Xr dhclient 8 .
57The file may contain extra tabs and newlines for formatting purposes.
58Keywords in the file are case-insensitive.
59Comments may be placed anywhere within the file (except within quotes).
60Comments begin with the
61.Sq #
62character and end at the end of the line.
63.Pp
64The
65.Nm
66file can be used to configure the behaviour of the client in a wide variety
67of ways: protocol timing, information requested from the server, information
68required of the server, defaults to use if the server does not provide
69certain information, values with which to override information provided by
70the server, or values to prepend or append to information provided by the
71server.
72The configuration file can also be preinitialized with addresses to
73use on networks that don't have DHCP servers.
74.Sh PROTOCOL TIMING
75The timing behaviour of the client need not be configured by the user.
76If no timing configuration is provided by the user, a fairly
77reasonable timing behaviour will be used by default \- one which
78results in fairly timely updates without placing an inordinate load on
79the server.
80.Pp
81The following statements can be used to adjust the timing behaviour of
82the DHCP client if required, however:
83.Bl -tag -width Ds
84.It Ic timeout Ar time ;
85The
86.Ic timeout
87statement determines the amount of time that must pass between the
88time that the client begins to try to determine its address and the
89time that it decides that it's not going to be able to contact a server.
90By default, this timeout is sixty seconds.
91After the timeout has passed, if there are any static leases defined in the
92configuration file, or any leases remaining in the lease database that
93have not yet expired, the client will loop through these leases
94attempting to validate them, and if it finds one that appears to be
95valid, it will use that lease's address.
96If there are no valid static leases or unexpired leases in the lease database,
97the client will restart the protocol after the defined retry interval.
98.It Ic retry Ar time ;
99The
100.Ic retry
101statement determines the time that must pass after the client has
102determined that there is no DHCP server present before it tries again
103to contact a DHCP server.
104By default, this is five minutes.
105.It Ic select-timeout Ar time ;
106It is possible (some might say desirable) for there to be more than
107one DHCP server serving any given network.
108In this case, it is possible that a client may be sent more than one offer
109in response to its initial lease discovery message.
110It may be that one of these offers is preferable to the other
111(e.g., one offer may have the address the client previously used,
112and the other may not).
113.Pp
114The
115.Ic select-timeout
116is the time after the client sends its first lease discovery request
117at which it stops waiting for offers from servers, assuming that it
118has received at least one such offer.
119If no offers have been received by the time the
120.Ic select-timeout
121has expired, the client will accept the first offer that arrives.
122.Pp
123By default, the
124.Ic select-timeout
125is zero seconds \- that is, the client will take the first offer it sees.
126.It Ic reboot Ar time ;
127When the client is restarted, it first tries to reacquire the last
128address it had.
129This is called the INIT-REBOOT state.
130If it is still attached to the same network it was attached to when it last
131ran, this is the quickest way to get started.
132The
133.Ic reboot
134statement sets the time that must elapse after the client first tries
135to reacquire its old address before it gives up and tries to discover
136a new address.
137By default, the reboot timeout is ten seconds.
138.It Ic backoff-cutoff Ar time ;
139The client uses an exponential backoff algorithm with some randomness,
140so that if many clients try to configure themselves at the same time,
141they will not make their requests in lockstep.
142The
143.Ic backoff-cutoff
144statement determines the maximum amount of time that the client is
145allowed to back off.
58c1d362 146It defaults to fifteen seconds.
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147.It Ic initial-interval Ar time ;
148The
149.Ic initial-interval
150statement sets the amount of time between the first attempt to reach a
151server and the second attempt to reach a server.
152Each time a message is sent, the interval between messages is incremented by
153twice the current interval multiplied by a random number between zero and one.
154If it is greater than the backoff-cutoff amount, it is set to that
155amount.
58c1d362 156It defaults to three seconds.
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157.It Ic link-timeout Ar time ;
158The
159.Ic link-timeout
160statement sets the amount of time to wait for an interface link before timing
161out.
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162The default value is ten seconds.
163The value zero requests that
58c1d362 164dhclient not wait for a link state change before timing out.
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165.El
166.Sh LEASE REQUIREMENTS AND REQUESTS
167The DHCP protocol allows the client to request that the server send it
168specific information, and not send it other information that it is not
169prepared to accept.
170The protocol also allows the client to reject offers from servers if they
171don't contain information the client needs, or if the information provided
172is not satisfactory.
173.Pp
174There is a variety of data contained in offers that DHCP servers send
175to DHCP clients.
176The data that can be specifically requested is what are called
177.Em DHCP Options .
178DHCP Options are defined in
179.Xr dhcp-options 5 .
180.Bl -tag -width Ds
181.It Xo
182.Ic request Op Ar option
183.Oo , Ar ... option Oc ;
184.Xc
185The
186.Ic request
187statement causes the client to request that any server responding to the
188client send the client its values for the specified options.
189Only the option names should be specified in the request statement \- not
190option parameters.
191.It Xo
192.Ic require Op Ar option
193.Oo , Ar ... option Oc ;
194.Xc
195The
196.Ic require
197statement lists options that must be sent in order for an offer to be accepted.
198Offers that do not contain all the listed options will be ignored.
199.It Xo
200.Ic send No { Op Ar option declaration
201.Oo , Ar ... option declaration Oc }
202.Xc
203The
204.Ic send
205statement causes the client to send the specified options to the server with
206the specified values.
207These are full option declarations as described in
208.Xr dhcp-options 5 .
209Options that are always sent in the DHCP protocol should not be specified
210here.
211One use for this statement is to send information to the server
212that will allow it to differentiate between this client and other
213clients or kinds of clients.
214.El
215.Sh OPTION MODIFIERS
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216Options in the lease can be modified before being passed to the client
217configuration script,
bbea0c93 218.Xr dhclient-script 8 .
4c9ce022 219.Pp
bbea0c93 220The default client configuration script
4c9ce022 221processes only options 1 (subnet
ee1dc8e7 222mask), 3 (routers), 6 (domain name servers), 15 (domain-name).
4c9ce022 223Use of option modifiers on other options will have no effect unless
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224.Xr dhclient-script 8
225the client configuration script is modified.
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226.Pp
227Several option modifiers are available.
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228.Bl -tag -width Ds
229.It Xo
230.Ic default No { Op Ar option declaration
231.Oo , Ar ... option declaration Oc }
232.Xc
233If for some set of options the client should use the value supplied by
234the server, but needs to use some default value if no value was supplied
235by the server, these values can be defined in the
236.Ic default
237statement.
238.It Xo
239.Ic supersede No { Op Ar option declaration
240.Oo , Ar ... option declaration Oc }
241.Xc
242If for some set of options the client should always use its own value
243rather than any value supplied by the server, these values can be defined
244in the
245.Ic supersede
246statement.
247.It Xo
248.Ic prepend No { Op Ar option declaration
249.Oo , Ar ... option declaration Oc }
250.Xc
251If for some set of options the client should use a value you supply,
252and then use the values supplied by the server, if any,
253these values can be defined in the
254.Ic prepend
255statement.
256The
257.Ic prepend
258statement can only be used for options which allow more than one value to
259be given.
260This restriction is not enforced \- if violated, the results are unpredictable.
261.It Xo
262.Ic append No { Op Ar option declaration
263.Oo , Ar ... option declaration Oc }
264.Xc
265If for some set of options the client should first use the values
266supplied by the server, if any, and then use values you supply, these
267values can be defined in the
268.Ic append
269statement.
270The
271.Ic append
272statement can only be used for options which allow more than one value to
273be given.
274This restriction is not enforced \- if you ignore it,
275the behaviour will be unpredictable.
276.El
277.Sh LEASE DECLARATIONS
278The lease declaration:
279.Pp
cf15b33a 280.D1 Ic lease No { Ar lease-declaration Oo Ar ... lease-declaration Oc }
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281.Pp
282The DHCP client may decide after some period of time (see
283.Sx PROTOCOL TIMING )
284that it is not going to succeed in contacting a server.
285At that time, it consults its own database of old leases and tests each one
286that has not yet timed out by pinging the listed router for that lease to
287see if that lease could work.
288It is possible to define one or more
289.Em fixed
290leases in the client configuration file for networks where there is no DHCP
291or BOOTP service, so that the client can still automatically configure its
292address.
293This is done with the
294.Ic lease
295statement.
296.Pp
297NOTE: the lease statement is also used in the
298.Pa dhclient.leases
299file in order to record leases that have been received from DHCP servers.
300Some of the syntax for leases as described below is only needed in the
301.Pa dhclient.leases
302file.
303Such syntax is documented here for completeness.
304.Pp
305A lease statement consists of the lease keyword, followed by a left
306curly brace, followed by one or more lease declaration statements,
307followed by a right curly brace.
308The following lease declarations are possible:
309.Bl -tag -width Ds
310.It Ic bootp ;
311The
312.Ic bootp
313statement is used to indicate that the lease was acquired using the
314BOOTP protocol rather than the DHCP protocol.
315It is never necessary to specify this in the client configuration file.
316The client uses this syntax in its lease database file.
317.It Ic interface Ar \&"string\&" ;
318The
319.Ic interface
320lease statement is used to indicate the interface on which the lease is valid.
321If set, this lease will only be tried on a particular interface.
322When the client receives a lease from a server, it always records the
323interface number on which it received that lease.
324If predefined leases are specified in the
325.Nm
326file, the interface should also be specified, although this is not required.
327.It Ic fixed-address Ar ip-address ;
328The
329.Ic fixed-address
330statement is used to set the IP address of a particular lease.
331This is required for all lease statements.
332The IP address must be specified as a dotted quad (e.g., 12.34.56.78).
333.It Ic filename Ar \&"string\&" ;
334The
335.Ic filename
336statement specifies the name of the boot filename to use.
337This is not used by the standard client configuration script, but is
338included for completeness.
339.It Ic server-name Ar \&"string\&" ;
340The
341.Ic server-name
342statement specifies the name of the boot server name to use.
343This is also not used by the standard client configuration script.
344.It Ic option Ar option-declaration ;
345The
346.Ic option
347statement is used to specify the value of an option supplied by the server,
348or, in the case of predefined leases declared in
68d52ec8 349.Nm ,
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350the value that the user wishes the client configuration script to use if the
351predefined lease is used.
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352.It Ic renew Ar date ;
353.It Ic rebind Ar date ;
354.It Ic expire Ar date ;
355The
356.Ic renew
357statement defines the time at which the DHCP client should begin trying to
358contact its server to renew a lease that it is using.
359The
360.Ic rebind
361statement defines the time at which the DHCP client should begin to try to
362contact
363.Em any
364DHCP server in order to renew its lease.
365The
366.Ic expire
367statement defines the time at which the DHCP client must stop using a lease
368if it has not been able to contact a server in order to renew it.
369.El
370.Pp
371These declarations are automatically set in leases acquired by the
372DHCP client, but must also be configured in predefined leases \- a
373predefined lease whose expiry time has passed will not be used by the
374DHCP client.
375.Pp
376Dates are specified as follows:
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377.Bd -ragged -offset indent
378.Ar <weekday>
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379.Sm off
380.Ar <year> No / Ar <month> No / Ar <day>
381.Ar <hour> : <minute> : <second>
382.Sm on
cf15b33a 383.Ed
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384.Pp
385The weekday is present to make it easy for a human to tell when a
386lease expires \- it's specified as a number from zero to six, with zero
387being Sunday.
388When declaring a predefined lease, it can always be specified as zero.
389The year is specified with the century, so it should generally be four
390digits except for really long leases.
391The month is specified as a number starting with 1 for January.
392The day of the month is likewise specified starting with 1.
393The hour is a number between 0 and 23,
394the minute a number between 0 and 59,
395and the second also a number between 0 and 59.
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396.Sh OTHER DECLARATIONS
397.Bl -tag -width Ds
398.It Ic reject Ar ip-address ;
399The
400.Ic reject
401statement causes the DHCP client to reject offers from servers who use
402the specified address as a server identifier.
403This can be used to avoid being configured by rogue or misconfigured DHCP
404servers, although it should be a last resort \- better to track down
405the bad DHCP server and fix it.
406.It Xo
407.Ic interface Ar \&"name\&" No { Ar declarations
408.Ar ... No }
409.Xc
410A client with more than one network interface may require different
411behaviour depending on which interface is being configured.
7cbe3601 412All timing parameters and declarations other than lease
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413declarations can be enclosed in an interface declaration, and those
414parameters will then be used only for the interface that matches the
415specified name.
416Interfaces for which there is no interface declaration will use the
417parameters declared outside of any interface declaration,
418or the default settings.
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419.It Ic script Ar \&"script-name\&" ;
420The
421.Ic script
bbea0c93 422statement is used to specify the pathname of the client configuration
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423script.
424This script is used by the DHCP client to set each interface's initial
425configuration prior to requesting an address, to test the address once it
426has been offered, and to set the interface's final configuration once a
427lease has been acquired.
428If no lease is acquired, the script is used to test predefined leases, if
429any, and also called once if no valid lease can be identified.
430For more information, see
431.Xr dhclient.leases 5 .
432.El
433.Sh EXAMPLES
434The following configuration file is used on a laptop
7cbe3601 435which has one interface, ep0 (a 3Com 3C589C).
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436Booting intervals have been shortened somewhat from the default, because
437the client is known to spend most of its time on networks with little DHCP
438activity.
439The laptop does roam to multiple networks.
440.Bd -literal -offset indent
441timeout 60;
442retry 60;
443reboot 10;
444select-timeout 5;
445initial-interval 2;
446reject 192.33.137.209;
447
448interface "ep0" {
449 send host-name "andare.fugue.com";
450 send dhcp-client-identifier 1:0:a0:24:ab:fb:9c;
451 send dhcp-lease-time 3600;
452 supersede domain-name "fugue.com rc.vix.com home.vix.com";
453 prepend domain-name-servers 127.0.0.1;
454 request subnet-mask, broadcast-address, time-offset, routers,
455 domain-name, domain-name-servers, host-name;
456 require subnet-mask, domain-name-servers;
457 script "/etc/dhclient-script";
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458}
459.Ed
460.Pp
461This is a very complicated
462.Nm
463file \- in general, yours should be much simpler.
464In many cases, it's sufficient to just create an empty
465.Nm
466file \- the defaults are usually fine.
467.Sh SEE ALSO
468.Xr dhclient.leases 5 ,
bbea0c93 469.Xr dhclient-script 8 ,
846204b6 470.Xr dhcp-options 5 ,
aa4e0df8 471.Xr dhcpd.conf 5 Pq Pa pkgsrc/net/isc-dhcpd4 ,
846204b6 472.Xr dhclient 8 ,
aa4e0df8 473.Xr dhcpd 8 Pq Pa pkgsrc/net/isc-dhcpd4
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474.Pp
475RFC 2132, RFC 2131.
476.Sh AUTHORS
477.An -nosplit
478.Xr dhclient 8
479was written by
480.An Ted Lemon Aq mellon@vix.com
481under a contract with Vixie Labs.
482.Pp
483The current implementation was reworked by
484.An Henning Brauer Aq henning@openbsd.org .