+.\" Copyright (c) 1983, 1991 The Regents of the University of California.
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\" must display the following acknowledgement:
+.\" This product includes software developed by the University of
+.\" California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\" may be used to endorse or promote products derived from this software
+.\" without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" @(#)ifconfig.8 6.13 (Berkeley) 3/16/91
+.\"
+.Dd March 16, 1991
+.Dt IFCONFIG 8
+.Os BSD 4.2
+.Sh NAME
+.Nm ifconfig
+.Nd configure network interface parameters
+.Sh SYNOPSIS
+.Nm ifconfig
+.Ar interface address_family
+.Oo
+.Ar address
+.Op Ar dest_address
+.Oc
+.Op Ar parameters
+.Nm ifconfig
+.Ar interface
+.Op Ar protocol_family
+.Sh DESCRIPTION
+.Nm Ifconfig
+is used to assign an address
+to a network interface and/or configure
+network interface parameters.
+.Nm Ifconfig
+must be used at boot time to define the network address
+of each interface present on a machine; it may also be used at
+a later time to redefine an interface's address
+or other operating parameters.
+.Pp
+Available operands for
+.Nm ifconfig:
+.Bl -tag -width Ds
+.It Ar Address
+For the
+.Tn DARPA-Internet
+family,
+the address is either a host name present in the host name data
+base,
+.Xr hosts 5 ,
+or a
+.Tn DARPA
+Internet address expressed in the Internet standard
+.Dq dot notation .
+For the Xerox Network Systems(tm) family,
+addresses are
+.Ar net:a.b.c.d.e.f ,
+where
+.Ar net
+is the assigned network number (in decimal),
+and each of the six bytes of the host number,
+.Ar a
+through
+.Ar f ,
+are specified in hexadecimal.
+The host number may be omitted on 10Mb/s Ethernet interfaces,
+which use the hardware physical address,
+and on interfaces other than the first.
+For the
+.Tn ISO
+family, addresses are specified as a long hexadecimal string,
+as in the Xerox family. However, two consecutive dots imply a zero
+byte, and the dots are optional, if the user wishes to (carefully)
+count out long strings of digits in network byte order.
+.It Ar address_family
+Specifies the
+.Ar address family
+which affects interpretation of the remaining parameters.
+Since an interface can receive transmissions in differing protocols
+with different naming schemes, specifying the address family is recommeded.
+The address or protocol families currently
+supported are
+.Dq inet ,
+.Dq iso ,
+and
+.Dq ns .
+.It Ar Interface
+The
+.Ar interface
+parameter is a string of the form
+.Dq name unit ,
+for example,
+.Dq en0
+.El
+.Pp
+The following parameters may be set with
+.Nm ifconfig :
+.Bl -tag -width dest_addressxx
+.It Cm alias
+Establish an additional network address for this interface.
+This is sometimes useful when changing network numbers, and
+one wishes to accept packets addressed to the old interface.
+.It Cm arp
+Enable the use of the Address Resolution Protocol in mapping
+between network level addresses and link level addresses (default).
+This is currently implemented for mapping between
+.Tn DARPA
+Internet
+addresses and 10Mb/s Ethernet addresses.
+.It Fl arp
+Disable the use of the Address Resolution Protocol.
+.It Cm broadcast
+(Inet only)
+Specify the address to use to represent broadcasts to the
+network.
+The default broadcast address is the address with a host part of all 1's.
+.It Cm debug
+Enable driver dependent debugging code; usually, this turns on
+extra console error logging.
+.It Fl debug
+Disable driver dependent debugging code.
+.It Cm delete
+Remove the network address specified.
+This would be used if you incorrectly specified an alias, or it
+was no longer needed.
+If you have incorrectly set an NS address having the side effect
+of specifying the host portion, removing all NS addresses will
+allow you to respecify the host portion.
+.It Cm dest_address
+Specify the address of the correspondent on the other end
+of a point to point link.
+.It Cm down
+Mark an interface ``down''. When an interface is
+marked ``down'', the system will not attempt to
+transmit messages through that interface.
+If possible, the interface will be reset to disable reception as well.
+This action does not automatically disable routes using the interface.
+.It Cm ipdst
+This is used to specify an Internet host who is willing to receive
+ip packets encapsulating NS packets bound for a remote network.
+An apparent point to point link is constructed, and
+the address specified will be taken as the NS address and network
+of the destination.
+IP encapsulation of
+.Tn CLNP
+packets is done differently.
+.It Cm metric Ar n
+Set the routing metric of the interface to
+.Ar n ,
+default 0.
+The routing metric is used by the routing protocol
+.Pq Xr routed 8 .
+Higher metrics have the effect of making a route
+less favorable; metrics are counted as addition hops
+to the destination network or host.
+.It Cm netmask Ar mask
+(Inet and Iso)
+Specify how much of the address to reserve for subdividing
+networks into sub-networks.
+The mask includes the network part of the local address
+and the subnet part, which is taken from the host field of the address.
+The mask can be specified as a single hexadecimal number
+with a leading 0x, with a dot-notation Internet address,
+or with a pseudo-network name listed in the network table
+.Xr networks 5 .
+The mask contains 1's for the bit positions in the 32-bit address
+which are to be used for the network and subnet parts,
+and 0's for the host part.
+The mask should contain at least the standard network portion,
+and the subnet field should be contiguous with the network
+portion.
+.\" see
+.\" Xr eon 5 .
+.It Cm nsellength Ar n
+.Pf ( Tn ISO
+only)
+This specifies a trailing number of bytes for a received
+.Tn NSAP
+used for local identification, the remaining leading part of which is
+taken to be the
+.Tn NET
+(Network Entity Title).
+The default value is 1, which is conformant to US
+.Tn GOSIP .
+When an iso address is set in an ifconfig command,
+it is really the
+.Tn NSAP
+which is being specified.
+For example, in
+.Tn US GOSIP ,
+20 hex digits should be
+specified in the
+.Tn ISO NSAP
+to be assigned to the interface.
+There is some evidence that a number different 1 may be useful
+for
+.Tn AFI
+37 type addresses.
+.It Cm trailers
+Request the use of a ``trailer'' link level encapsulation when
+sending (default).
+If a network interface supports
+.Cm trailers ,
+the system will, when possible, encapsulate outgoing
+messages in a manner which minimizes the number of
+memory to memory copy operations performed by the receiver.
+On networks that support the Address Resolution Protocol (see
+.Xr arp 4 ;
+currently, only 10 Mb/s Ethernet),
+this flag indicates that the system should request that other
+systems use trailers when sending to this host.
+Similarly, trailer encapsulations will be sent to other
+hosts that have made such requests.
+Currently used by Internet protocols only.
+.It Fl trailers
+Disable the use of a ``trailer'' link level encapsulation.
+.It Cm up
+Mark an interface ``up''.
+This may be used to enable an interface after an ``ifconfig down.''
+It happens automatically when setting the first address on an interface.
+If the interface was reset when previously marked down,
+the hardware will be re-initialized.
+.El
+.Pp
+.Pp
+.Nm Ifconfig
+displays the current configuration for a network interface
+when no optional parameters are supplied.
+If a protocol family is specified,
+Ifconfig will report only the details specific to that protocol family.
+.Pp
+Only the super-user may modify the configuration of a network interface.
+.Sh DIAGNOSTICS
+Messages indicating the specified interface does not exit, the
+requested address is unknown, or the user is not privileged and
+tried to alter an interface's configuration.
+.Sh SEE ALSO
+.Xr netstat 1 ,
+.Xr netintro 4 ,
+.Xr rc 8 ,
+.Xr routed 8 ,
+.\" .Xr eon 5
+.Sh HISTORY
+The
+.Nm
+command appeared in
+.Bx 4.2 .
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