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DHCLIENT(8)

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NAME    [Toc]    [Back]

     dhclient - Dynamic Host Configuration Protocol (DHCP) Client

SYNOPSIS    [Toc]    [Back]

     dhclient [-dqu] [-c file] [-l file] interface

DESCRIPTION    [Toc]    [Back]

     The  dhclient  utility provides a means for configuring network interfaces
     using DHCP, BOOTP, or if these protocols fail, by statically
assigning an
     address.

     The  name  of the network interface that dhclient should attempt to configure
 must be specified on the command line.

     The options are as follows:

     -c file  Specify an alternate location, file, for  the  configuration file.

     -d        Forces dhclient to always run as a foreground process.  By default,
 dhclient runs in the foreground until it has
configured
              the  interface,  and then will revert to running in
the background.


     -l file  Specify an alternate location, file, for the leases
file.

     -q       Forces dhclient to be less verbose on startup.

     -u        Forces  dhclient to reject leases with unknown options in them.
              The default behaviour is to accept such  lease  offers.

     The  DHCP protocol allows a host to contact a central server
which maintains
 a list of IP addresses which may be assigned on one or
more subnets.
   A DHCP client may request an address from this pool,
and then use
     it on a temporary basis for communication  on  the  network.
The DHCP protocol
  also  provides a mechanism whereby a client can learn
important details
 about the network to which it is attached, such as the
location of
     a  default router, the location of a name server, and so on.

     On startup, dhclient reads /etc/dhclient.conf for configuration instructions.
   It  then  gets a list of all the network interfaces
that are configured
 in the current system.  It then attempts to  configure each interface
 with DHCP.

     In  order  to keep track of leases across system reboots and
server
     restarts, dhclient keeps a list of leases it  has  been  assigned in the
     /var/db/dhclient.leases.IFNAME  file.   "IFNAME"  represents
the network interface
 of the DHCP client (e.g. em0), one for  each  interface.  On startup,
  after reading the dhclient.conf(5) file, dhclient reads
the leases
     file to refresh its memory about what leases it has been assigned.

     Old  leases  are  kept around in case the DHCP server is unavailable when
     dhclient is first invoked (generally during the initial system boot process).
     In    that    event,    old   leases   from   the
dhclient.leases.IFNAME file
     which have not yet expired are tested, and if they  are  determined to be
     valid,  they  are  used until either they expire or the DHCP
server becomes
     available.

     A mobile host which may sometimes need to access  a  network
on which no
     DHCP server exists may be preloaded with a lease for a fixed
address on
     that network.  When all attempts to contact  a  DHCP  server
have failed,
     dhclient  will  try  to validate the static lease, and if it
succeeds, it
     will use that lease until it is restarted.

     A mobile host may also travel to some networks on which DHCP
is not
     available  but  BOOTP  is.  In that case, it may be advantageous to arrange
     with the network administrator for an  entry  on  the  BOOTP
database, so
     that  the  host can boot quickly on that network rather than
cycling
     through the list of old leases.

NOTES    [Toc]    [Back]

     You must have the Berkeley Packet Filter (BPF) configured in
your kernel.
     dhclient  requires  at  least  one  /dev/bpf*  file for each
broadcast network
     interface that is attached to your system.  See  bpf(4)  for
more information.

FILES    [Toc]    [Back]

     /etc/dhclient.conf                DHCP  client configuration
file
     /var/db/dhclient.leases.IFNAME   database of acquired leases

SEE ALSO    [Toc]    [Back]

      
      
     dhclient.conf(5),   dhclient.leases(5),  dhclient-script(8),
dhcp(8),
     dhcpd(8), dhcrelay(8)

AUTHORS    [Toc]    [Back]

     dhclient was written by Ted Lemon <mellon@fugue.com> and
     Elliot Poger <elliot@poger.com>.

     The current implementation was reworked by
     Henning Brauer <henning@openbsd.org>.

OpenBSD     3.6                           April      7,      2004
[ Back ]
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