1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)ifconfig.8 8.3 (Berkeley) 1/5/94 33.\" 34.Dd January 5, 1994 35.Dt IFCONFIG 8 36.Os BSD 4.2 37.Sh NAME 38.Nm ifconfig 39.Nd configure network interface parameters 40.Sh SYNOPSIS 41.Nm ifconfig 42.Ar interface address_family 43.Oo 44.Ar address 45.Op Ar dest_address 46.Oc 47.Op Ar parameters 48.Nm ifconfig 49.Ar interface 50.Op Ar protocol_family 51.Nm ifconfig 52.Ar -a 53.Nm ifconfig 54.Ar -au 55.Nm ifconfig 56.Ar -ad 57.Sh DESCRIPTION 58.Nm Ifconfig 59is used to assign an address 60to a network interface and/or configure 61network interface parameters. 62.Nm Ifconfig 63must be used at boot time to define the network address 64of each interface present on a machine; it may also be used at 65a later time to redefine an interface's address 66or other operating parameters. 67.Pp 68Available operands for 69.Nm ifconfig: 70.Bl -tag -width Ds 71.It Ar Address 72For the 73.Tn DARPA-Internet 74family, 75the address is either a host name present in the host name data 76base, 77.Xr hosts 5 , 78or a 79.Tn DARPA 80Internet address expressed in the Internet standard 81.Dq dot notation . 82For the Xerox Network Systems(tm) family, 83addresses are 84.Ar net:a.b.c.d.e.f , 85where 86.Ar net 87is the assigned network number (in decimal), 88and each of the six bytes of the host number, 89.Ar a 90through 91.Ar f , 92are specified in hexadecimal. 93The host number may be omitted on 10Mb/s Ethernet interfaces, 94which use the hardware physical address, 95and on interfaces other than the first. 96For the 97.Tn ISO 98family, addresses are specified as a long hexadecimal string, 99as in the Xerox family. However, two consecutive dots imply a zero 100byte, and the dots are optional, if the user wishes to (carefully) 101count out long strings of digits in network byte order. 102.It Ar address_family 103Specifies the 104.Ar address family 105which affects interpretation of the remaining parameters. 106Since an interface can receive transmissions in differing protocols 107with different naming schemes, specifying the address family is recommeded. 108The address or protocol families currently 109supported are 110.Dq inet , 111.Dq iso , 112and 113.Dq ns . 114.It Ar Interface 115The 116.Ar interface 117parameter is a string of the form 118.Dq name unit , 119for example, 120.Dq en0 121.El 122.Pp 123The following parameters may be set with 124.Nm ifconfig : 125.Bl -tag -width dest_addressxx 126.It Cm alias 127Establish an additional network address for this interface. 128This is sometimes useful when changing network numbers, and 129one wishes to accept packets addressed to the old interface. 130.It Cm arp 131Enable the use of the Address Resolution Protocol in mapping 132between network level addresses and link level addresses (default). 133This is currently implemented for mapping between 134.Tn DARPA 135Internet 136addresses and 10Mb/s Ethernet addresses. 137.It Fl arp 138Disable the use of the Address Resolution Protocol. 139.It Cm broadcast 140(Inet only) 141Specify the address to use to represent broadcasts to the 142network. 143The default broadcast address is the address with a host part of all 1's. 144.It Cm debug 145Enable driver dependent debugging code; usually, this turns on 146extra console error logging. 147.It Fl debug 148Disable driver dependent debugging code. 149.It Cm delete 150Remove the network address specified. 151This would be used if you incorrectly specified an alias, or it 152was no longer needed. 153If you have incorrectly set an NS address having the side effect 154of specifying the host portion, removing all NS addresses will 155allow you to respecify the host portion. 156.It Cm dest_address 157Specify the address of the correspondent on the other end 158of a point to point link. 159.It Cm down 160Mark an interface ``down''. When an interface is 161marked ``down'', the system will not attempt to 162transmit messages through that interface. 163If possible, the interface will be reset to disable reception as well. 164This action does not automatically disable routes using the interface. 165.It Cm ipdst 166This is used to specify an Internet host who is willing to receive 167ip packets encapsulating NS packets bound for a remote network. 168An apparent point to point link is constructed, and 169the address specified will be taken as the NS address and network 170of the destination. 171IP encapsulation of 172.Tn CLNP 173packets is done differently. 174.It Cm metric Ar n 175Set the routing metric of the interface to 176.Ar n , 177default 0. 178The routing metric is used by the routing protocol 179.Pq Xr routed 8 . 180Higher metrics have the effect of making a route 181less favorable; metrics are counted as addition hops 182to the destination network or host. 183.It Cm mtu Ar n 184Set the maximum transmission unit of the interface to 185.Ar n , 186default is interface specific. 187The mtu is used to limit the size of packets that are transmitted on an 188interface. 189Not all interfaces support setting the mtu, and some interfaces have 190range restrictions. 191.It Cm netmask Ar mask 192(Inet and ISO) 193Specify how much of the address to reserve for subdividing 194networks into sub-networks. 195The mask includes the network part of the local address 196and the subnet part, which is taken from the host field of the address. 197The mask can be specified as a single hexadecimal number 198with a leading 0x, with a dot-notation Internet address, 199or with a pseudo-network name listed in the network table 200.Xr networks 5 . 201The mask contains 1's for the bit positions in the 32-bit address 202which are to be used for the network and subnet parts, 203and 0's for the host part. 204The mask should contain at least the standard network portion, 205and the subnet field should be contiguous with the network 206portion. 207.\" see 208.\" Xr eon 5 . 209.It Cm nsellength Ar n 210.Pf ( Tn ISO 211only) 212This specifies a trailing number of bytes for a received 213.Tn NSAP 214used for local identification, the remaining leading part of which is 215taken to be the 216.Tn NET 217(Network Entity Title). 218The default value is 1, which is conformant to US 219.Tn GOSIP . 220When an ISO address is set in an ifconfig command, 221it is really the 222.Tn NSAP 223which is being specified. 224For example, in 225.Tn US GOSIP , 22620 hex digits should be 227specified in the 228.Tn ISO NSAP 229to be assigned to the interface. 230There is some evidence that a number different from 1 may be useful 231for 232.Tn AFI 23337 type addresses. 234.It Cm trailers 235Request the use of a ``trailer'' link level encapsulation when 236sending (default). 237If a network interface supports 238.Cm trailers , 239the system will, when possible, encapsulate outgoing 240messages in a manner which minimizes the number of 241memory to memory copy operations performed by the receiver. 242On networks that support the Address Resolution Protocol (see 243.Xr arp 4 ; 244currently, only 10 Mb/s Ethernet), 245this flag indicates that the system should request that other 246systems use trailers when sending to this host. 247Similarly, trailer encapsulations will be sent to other 248hosts that have made such requests. 249Currently used by Internet protocols only. 250.It Fl trailers 251Disable the use of a ``trailer'' link level encapsulation. 252.It Cm link[0-2] 253Enable special processing of the link level of the interface. 254These three options are interface specific in actual effect, however, 255they are in general used to select special modes of operation. An example 256of this is to enable SLIP compression. Currently, only used by SLIP. 257.It Fl link[0-2] 258Disable special processing at the link level with the specified interface. 259.It Cm up 260Mark an interface ``up''. 261This may be used to enable an interface after an ``ifconfig down.'' 262It happens automatically when setting the first address on an interface. 263If the interface was reset when previously marked down, 264the hardware will be re-initialized. 265.El 266.Pp 267.Pp 268.Nm Ifconfig 269.Ar -a 270displays information on all interfaces. When followed by a configuration 271parameter, it will also set the configuration on all interfaces. 272.Pp 273.Nm Ifconfig 274.Ar -au 275is similar to 276.Nm ifconfig 277.Ar -a , 278except it only affects interfaces that are currently marked as up. 279Conversely, 280.Nm ifconfig 281.Ar -ad 282affects only interfaces that are marked down. 283.Pp 284.Nm Ifconfig 285displays the current configuration for a network interface 286when no optional parameters are supplied. 287If a protocol family is specified, 288Ifconfig will report only the details specific to that protocol family. 289.Pp 290Only the super-user may modify the configuration of a network interface. 291.Sh DIAGNOSTICS 292Messages indicating the specified interface does not exit, the 293requested address is unknown, or the user is not privileged and 294tried to alter an interface's configuration. 295.Sh SEE ALSO 296.Xr netstat 1 , 297.Xr netintro 4 , 298.Xr rc 8 , 299.Xr routed 8 , 300.\" .Xr eon 5 301.Sh HISTORY 302The 303.Nm 304command appeared in 305.Bx 4.2 . 306