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.\" 4. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" From: @(#)ifconfig.8 8.3 (Berkeley) 1/5/94 29.\" $FreeBSD: src/sbin/ifconfig/ifconfig.8,v 1.85 2004/07/27 09:51:49 yar Exp $ 30.\" $DragonFly: src/sbin/ifconfig/ifconfig.8,v 1.7 2005/04/25 17:33:26 swildner Exp $ 31.\" 32.Dd July 26, 2004 33.Dt IFCONFIG 8 34.Os 35.Sh NAME 36.Nm ifconfig 37.Nd configure network interface parameters 38.Sh SYNOPSIS 39.Nm 40.Op Fl L 41.Op Fl m 42.Ar interface 43.Op Cm create 44.Op Ar address_family 45.Oo 46.Ar address 47.Op Ar dest_address 48.Oc 49.Op Ar parameters 50.Nm 51.Ar interface 52.Cm destroy 53.Nm 54.Fl a 55.Op Fl L 56.Op Fl d 57.Op Fl m 58.Op Fl u 59.Op Ar address_family 60.Nm 61.Fl l 62.Op Fl d 63.Op Fl u 64.Op Ar address_family 65.Nm 66.Op Fl L 67.Op Fl d 68.Op Fl m 69.Op Fl u 70.Op Fl C 71.Sh DESCRIPTION 72The 73.Nm 74utility is used to assign an address 75to a network interface and/or configure 76network interface parameters. 77The 78.Nm 79utility must be used at boot time to define the network address 80of each interface present on a machine; it may also be used at 81a later time to redefine an interface's address 82or other operating parameters. 83.Pp 84The following options are available: 85.Bl -tag -width indent 86.It Ar address 87For the 88.Tn DARPA Ns -Internet 89family, 90the address is either a host name present in the host name data 91base, 92.Xr hosts 5 , 93or a 94.Tn DARPA 95Internet address expressed in the Internet standard 96.Dq dot notation . 97.Pp 98It is also possible to use the CIDR notation (also known as the 99slash notation) to include the netmask. 100That is, one can specify an address like 101.Li 192.168.0.1/16 . 102.Pp 103For 104.Dq inet6 105family, it is also possible to specify the prefix length using the slash 106notation, like 107.Li ::1/128 . 108See the 109.Cm prefixlen 110parameter below for more information. 111.\" For the Xerox Network Systems(tm) family, 112.\" addresses are 113.\" .Ar net:a.b.c.d.e.f , 114.\" where 115.\" .Ar net 116.\" is the assigned network number (in decimal), 117.\" and each of the six bytes of the host number, 118.\" .Ar a 119.\" through 120.\" .Ar f , 121.\" are specified in hexadecimal. 122.\" The host number may be omitted on IEEE 802 protocol 123.\" (Ethernet, FDDI, and Token Ring) interfaces, 124.\" which use the hardware physical address, 125.\" and on interfaces other than the first. 126.\" For the 127.\" .Tn ISO 128.\" family, addresses are specified as a long hexadecimal string, 129.\" as in the Xerox family. 130.\" However, two consecutive dots imply a zero 131.\" byte, and the dots are optional, if the user wishes to (carefully) 132.\" count out long strings of digits in network byte order. 133.Pp 134The link-level 135.Pq Dq link 136address 137is specified as a series of colon-separated hex digits. 138This can be used to 139e.g.\& set a new MAC address on an ethernet interface, though the 140mechanism used is not ethernet-specific. 141If the interface is already 142up when this option is used, it will be briefly brought down and 143then brought back up again in order to ensure that the receive 144filter in the underlying ethernet hardware is properly reprogrammed. 145.It Ar address_family 146Specify the 147address family 148which affects interpretation of the remaining parameters. 149Since an interface can receive transmissions in differing protocols 150with different naming schemes, specifying the address family is recommended. 151The address or protocol families currently 152supported are 153.Dq inet , 154.Dq inet6 , 155.Dq atalk , 156.Dq ipx , 157.\" .Dq iso , 158and 159.Dq link . 160.\" and 161.\" .Dq ns . 162The default is 163.Dq inet . 164.Dq ether 165and 166.Dq lladdr 167are synonyms for 168.Dq link . 169.It Ar dest_address 170Specify the address of the correspondent on the other end 171of a point to point link. 172.It Ar interface 173This 174parameter is a string of the form 175.Dq name unit , 176for example, 177.Dq Li ed0 . 178.El 179.Pp 180The following parameters may be set with 181.Nm : 182.Bl -tag -width indent 183.It Cm add 184Another name for the 185.Cm alias 186parameter. 187Introduced for compatibility 188with 189.Bsx . 190.It Cm alias 191Establish an additional network address for this interface. 192This is sometimes useful when changing network numbers, and 193one wishes to accept packets addressed to the old interface. 194If the address is on the same subnet as the first network address 195for this interface, a non-conflicting netmask must be given. 196Usually 197.Li 0xffffffff 198is most appropriate. 199.It Fl alias 200Remove the network address specified. 201This would be used if you incorrectly specified an alias, or it 202was no longer needed. 203If you have incorrectly set an NS address having the side effect 204of specifying the host portion, removing all NS addresses will 205allow you to respecify the host portion. 206.It Cm anycast 207(Inet6 only.) 208Specify that the address configured is an anycast address. 209Based on the current specification, 210only routers may configure anycast addresses. 211Anycast address will not be used as source address of any of outgoing 212IPv6 packets. 213.It Cm arp 214Enable the use of the Address Resolution Protocol 215.Pq Xr arp 4 216in mapping 217between network level addresses and link level addresses (default). 218This is currently implemented for mapping between 219.Tn DARPA 220Internet 221addresses and 222.Tn IEEE 223802 48-bit MAC addresses (Ethernet, FDDI, and Token Ring addresses). 224.It Fl arp 225Disable the use of the Address Resolution Protocol 226.Pq Xr arp 4 . 227.It Cm broadcast 228(Inet only.) 229Specify the address to use to represent broadcasts to the 230network. 231The default broadcast address is the address with a host part of all 1's. 232.It Cm debug 233Enable driver dependent debugging code; usually, this turns on 234extra console error logging. 235.It Fl debug 236Disable driver dependent debugging code. 237.It Cm promisc 238Put interface into permanently promiscuous mode. 239.It Fl promisc 240Disable permanently promiscuous mode. 241.It Cm delete 242Another name for the 243.Fl alias 244parameter. 245.It Cm down 246Mark an interface 247.Dq down . 248When an interface is marked 249.Dq down , 250the system will not attempt to 251transmit messages through that interface. 252If possible, the interface will be reset to disable reception as well. 253This action does not automatically disable routes using the interface. 254.It Cm eui64 255(Inet6 only.) 256Fill interface index 257(lowermost 64bit of an IPv6 address) 258automatically. 259.\" .It Cm ipdst 260.\" This is used to specify an Internet host who is willing to receive 261.\" ip packets encapsulating NS packets bound for a remote network. 262.\" An apparent point to point link is constructed, and 263.\" the address specified will be taken as the NS address and network 264.\" of the destination. 265.\" IP encapsulation of 266.\" .Tn CLNP 267.\" packets is done differently. 268.It Cm media Ar type 269If the driver supports the media selection system, set the media type 270of the interface to 271.Ar type . 272Some interfaces support the mutually exclusive use of one of several 273different physical media connectors. 274For example, a 10Mb/s Ethernet 275interface might support the use of either 276.Tn AUI 277or twisted pair connectors. 278Setting the media type to 279.Dq Li 10base5/AUI 280would change the currently active connector to the AUI port. 281Setting it to 282.Dq Li 10baseT/UTP 283would activate twisted pair. 284Refer to the interfaces' driver 285specific documentation or man page for a complete list of the 286available types. 287.It Cm mediaopt Ar opts 288If the driver supports the media selection system, set the specified 289media options on the interface. 290The 291.Ar opts 292argument 293is a comma delimited list of options to apply to the interface. 294Refer to the interfaces' driver specific man page for a complete 295list of available options. 296.It Fl mediaopt Ar opts 297If the driver supports the media selection system, disable the 298specified media options on the interface. 299.It Cm mode Ar mode 300If the driver supports the media selection system, set the specified 301operating mode on the interface to 302.Ar mode . 303For IEEE 802.11 wireless interfaces that support multiple operating modes 304this directive is used to select between 802.11a 305.Pq Dq Li 11a , 306802.11b 307.Pq Dq Li 11b , 308and 802.11g 309.Pq Dq Li 11g 310operating modes. 311.It Cm name Ar name 312Set the interface name to 313.Ar name . 314.It Cm rxcsum , txcsum 315If the driver supports user-configurable checksum offloading, 316enable receive (or transmit) checksum offloading on the interface. 317Some drivers may not be able to enable these flags independently 318of each other, so setting one may also set the other. 319The driver will offload as much checksum work as it can reliably 320support, the exact level of offloading varies between drivers. 321.\".It Fl rxcsum , Fl txcsum 322.\"If the driver supports user-configurable checksum offloading, 323.\"disable receive (or transmit) checksum offloading on the interface. 324.\"These settings may not always be independent of each other. 325.\".It Cm polling 326.\"If the driver has user-configurable 327.\".Xr polling 4 328.\"support, select the polling mode on the interface. 329.\".It Fl polling 330.\"If the driver has user-configurable 331.\".Xr polling 4 332.\"support, select the interrupt mode on the interface. 333.It Cm tunnel Ar src_addr dest_addr 334(IP tunnel devices only.) 335Configure the physical source and destination address for IP tunnel 336interfaces 337.Pq Xr gif 4 . 338The arguments 339.Ar src_addr 340and 341.Ar dest_addr 342are interpreted as the outer source/destination for the encapsulating 343IPv4/IPv6 header. 344.It Cm deletetunnel 345Unconfigure the physical source and destination address for IP tunnel 346interfaces previously configured with 347.Cm tunnel . 348.It Cm create 349Create the specified network pseudo-device. 350If the interface is given without a unit number, try to create a new 351device with an arbitrary unit number. 352If creation of an arbitrary device is successful, the new device name is 353printed to standard output. 354.It Cm destroy 355Destroy the specified network pseudo-device. 356.It Cm plumb 357Another name for the 358.Cm create 359parameter. 360Included for 361.Tn Solaris 362compatibility. 363.It Cm unplumb 364Another name for the 365.Cm destroy 366parameter. 367Included for 368.Tn Solaris 369compatibility. 370.It Cm vlan Ar vlan_tag 371If the interface is a 372.Xr vlan 4 373pseudo interface, set the VLAN tag value 374to 375.Ar vlan_tag . 376This value is a 16-bit number which is used to create an 802.1Q 377VLAN header for packets sent from the 378.Xr vlan 4 379interface. 380Note that 381.Cm vlan 382and 383.Cm vlandev 384must both be set at the same time. 385.It Cm vlandev Ar iface 386If the interface is a 387.Xr vlan 4 388pseudo device, associate physical interface 389.Ar iface 390with it. 391Packets transmitted through the 392.Xr vlan 4 393interface will be 394diverted to the specified physical interface 395.Ar iface 396with 802.1Q VLAN encapsulation. 397Packets with 802.1Q encapsulation received 398by the parent interface with the correct VLAN tag will be diverted to 399the associated 400.Xr vlan 4 401pseudo-interface. 402The 403.Xr vlan 4 404interface is assigned a 405copy of the parent interface's flags and the parent's ethernet address. 406The 407.Cm vlandev 408and 409.Cm vlan 410must both be set at the same time. 411If the 412.Xr vlan 4 413interface already has 414a physical interface associated with it, this command will fail. 415To 416change the association to another physical interface, the existing 417association must be cleared first. 418.Pp 419Note: if the hardware tagging capability 420is set on the parent interface, the 421.Xr vlan 4 422pseudo 423interface's behavior changes: 424the 425.Xr vlan 4 426interface recognizes that the 427parent interface supports insertion and extraction of VLAN tags on its 428own (usually in firmware) and that it should pass packets to and from 429the parent unaltered. 430.It Fl vlandev Ar iface 431If the driver is a 432.Xr vlan 4 433pseudo device, disassociate the physical interface 434.Ar iface 435from it. 436This breaks the link between the 437.Xr vlan 4 438interface and its parent, 439clears its VLAN tag, flags and its link address and shuts the interface down. 440.It Cm vlanmtu , vlanhwtag 441If the driver offers user-configurable VLAN support, enable 442reception of extended frames or tag processing in hardware, 443respectively. 444Note that this must be issued on a physical interface associated with 445.Xr vlan 4 , 446not on a 447.Xr vlan 4 448interface itself. 449.It Fl vlanmtu , Fl vlanhwtag 450If the driver offers user-configurable VLAN support, disable 451reception of extended frames or tag processing in hardware, 452respectively. 453.It Cm metric Ar n 454Set the routing metric of the interface to 455.Ar n , 456default 0. 457The routing metric is used by the routing protocol 458.Pq Xr routed 8 . 459Higher metrics have the effect of making a route 460less favorable; metrics are counted as addition hops 461to the destination network or host. 462.It Cm mtu Ar n 463Set the maximum transmission unit of the interface to 464.Ar n , 465default is interface specific. 466The MTU is used to limit the size of packets that are transmitted on an 467interface. 468Not all interfaces support setting the MTU, and some interfaces have 469range restrictions. 470.It Cm netmask Ar mask 471.\" (Inet and ISO.) 472(Inet only.) 473Specify how much of the address to reserve for subdividing 474networks into sub-networks. 475The mask includes the network part of the local address 476and the subnet part, which is taken from the host field of the address. 477The mask can be specified as a single hexadecimal number 478with a leading 479.Ql 0x , 480with a dot-notation Internet address, 481or with a pseudo-network name listed in the network table 482.Xr networks 5 . 483The mask contains 1's for the bit positions in the 32-bit address 484which are to be used for the network and subnet parts, 485and 0's for the host part. 486The mask should contain at least the standard network portion, 487and the subnet field should be contiguous with the network 488portion. 489.Pp 490The netmask can also be specified in CIDR notation after the address. 491See the 492.Ar address 493option above for more information. 494.It Cm prefixlen Ar len 495(Inet6 only.) 496Specify that 497.Ar len 498bits are reserved for subdividing networks into sub-networks. 499The 500.Ar len 501must be integer, and for syntactical reason it must be between 0 to 128. 502It is almost always 64 under the current IPv6 assignment rule. 503If the parameter is omitted, 64 is used. 504.Pp 505The prefix can also be specified using the slash notation after the address. 506See the 507.Ar address 508option above for more information. 509.\" see 510.\" Xr eon 5 . 511.\" .It Cm nsellength Ar n 512.\" .Pf ( Tn ISO 513.\" only) 514.\" This specifies a trailing number of bytes for a received 515.\" .Tn NSAP 516.\" used for local identification, the remaining leading part of which is 517.\" taken to be the 518.\" .Tn NET 519.\" (Network Entity Title). 520.\" The default value is 1, which is conformant to US 521.\" .Tn GOSIP . 522.\" When an ISO address is set in an ifconfig command, 523.\" it is really the 524.\" .Tn NSAP 525.\" which is being specified. 526.\" For example, in 527.\" .Tn US GOSIP , 528.\" 20 hex digits should be 529.\" specified in the 530.\" .Tn ISO NSAP 531.\" to be assigned to the interface. 532.\" There is some evidence that a number different from 1 may be useful 533.\" for 534.\" .Tn AFI 535.\" 37 type addresses. 536.It Cm range Ar netrange 537Under appletalk, set the interface to respond to a 538.Ar netrange 539of the form 540.Ar startnet Ns - Ns Ar endnet . 541Appletalk uses this scheme instead of 542netmasks though 543.Fx 544implements it internally as a set of netmasks. 545.It Cm remove 546Another name for the 547.Fl alias 548parameter. 549Introduced for compatibility 550with 551.Bsx . 552.It Cm phase 553The argument following this specifies the version (phase) of the 554Appletalk network attached to the interface. 555Values of 1 or 2 are permitted. 556.Sm off 557.It Cm link Op Cm 0 No - Cm 2 558.Sm on 559Enable special processing of the link level of the interface. 560These three options are interface specific in actual effect, however, 561they are in general used to select special modes of operation. 562An example 563of this is to enable SLIP compression, or to select the connector type 564for some Ethernet cards. 565Refer to the man page for the specific driver 566for more information. 567.Sm off 568.It Fl link Op Cm 0 No - Cm 2 569.Sm on 570Disable special processing at the link level with the specified interface. 571.\".It Cm monitor 572.\"Put the interface in monitor mode. 573.\"No packets are transmitted, and received packets are discarded after 574.\".Xr bpf 4 575.\"processing. 576.\".It Fl monitor 577.\"Take the interface out of monitor mode. 578.It Cm up 579Mark an interface 580.Dq up . 581This may be used to enable an interface after an 582.Dq Nm Cm down . 583It happens automatically when setting the first address on an interface. 584If the interface was reset when previously marked down, 585the hardware will be re-initialized. 586.It Cm ssid Ar ssid 587For IEEE 802.11 wireless interfaces, set the desired Service Set 588Identifier (aka network name). 589The SSID is a string up to 32 characters 590in length and may be specified as either a normal string or in 591hexadecimal when proceeded by 592.Ql 0x . 593Additionally, the SSID may be cleared by setting it to 594.Ql - . 595.It Cm nwid Ar ssid 596Another name for the 597.Cm ssid 598parameter. 599Included for 600.Nx 601compatibility. 602.It Cm stationname Ar name 603For IEEE 802.11 wireless interfaces, set the name of this station. 604It appears that the station name is not really part of the IEEE 802.11 605protocol though all interfaces seem to support it. 606As such it only 607seems to be meaningful to identical or virtually identical equipment. 608Setting the station name is identical in syntax to setting the SSID. 609.It Cm station Ar name 610Another name for the 611.Cm stationname 612parameter. 613Included for 614.Bsx 615compatibility. 616.It Cm channel Ar number 617For IEEE 802.11 wireless interfaces, set the desired channel. 618Channels range from 1 to 14, but the exact selection available 619depends on the region your adaptor was manufactured for. 620Setting 621the channel to 0 will give you the default for your adaptor. 622Many 623adaptors ignore this setting unless you are in ad-hoc mode. 624.It Cm authmode Ar mode 625For IEEE 802.11 wireless interfaces, set the desired authentication mode 626in infrastructure mode. 627Not all adaptors support all modes. 628The set of 629valid modes is 630.Dq Li none , 631.Dq Li open , 632and 633.Dq Li shared . 634Modes are case insensitive. 635.It Cm powersave 636For IEEE 802.11 wireless interfaces, enable powersave mode. 637.It Fl powersave 638For IEEE 802.11 wireless interfaces, disable powersave mode. 639.It Cm powersavesleep Ar sleep 640For IEEE 802.11 wireless interfaces, set the desired max powersave sleep 641time in milliseconds. 642.It Cm protmode Ar technique 643For IEEE 802.11 wireless interfaces operating in 11g, use the specified 644.Ar technique 645for protecting OFDM frames in a mixed 11b/11g network. 646The set of valid techniques is 647.Dq Li off , 648.Dq Li cts 649(CTS to self), 650and 651.Dq Li rtscts 652(RTS/CTS). 653Technique names are case insensitive. 654.It Cm rtsthreshold Ar length 655For IEEE 802.11 wireless interfaces, set the threshold for which 656transmitted frames are preceded by transmission of an 657RTS 658control frame. 659The 660.Ar length 661argument 662is the frame size in bytes and must be in the range 1 to 2312. 663Not all adaptors support setting the RTS threshold. 664.It Cm txpower Ar power 665For IEEE 802.11 wireless interfaces, set the power used to transmit frames. 666The 667.Ar power 668argument 669is a unitless value in the range 0 to 100 that is interpreted 670by drivers to derive a device-specific value. 671Out of range values are truncated. 672Typically only a few discreet power settings are available and 673the driver will use the setting closest to the specified value. 674Not all adaptors support changing the transmit power. 675.It Cm wepmode Ar mode 676For IEEE 802.11 wireless interfaces, set the desired WEP mode. 677Not all adaptors support all modes. 678The set of valid modes is 679.Dq Li off , 680.Dq Li on , 681and 682.Dq Li mixed . 683The 684.Dq Li mixed 685mode explicitly tells the adaptor to allow association with access 686points which allow both encrypted and unencrypted traffic. 687On these adaptors, 688.Dq Li on 689means that the access point must only allow encrypted connections. 690On other adaptors, 691.Dq Li on 692is generally another name for 693.Dq Li mixed . 694Modes are case insensitive. 695.It Cm weptxkey Ar index 696For IEEE 802.11 wireless interfaces, set the WEP key to be used for 697transmission. 698.It Cm wepkey Ar key Ns | Ns Ar index : Ns Ar key 699For IEEE 802.11 wireless interfaces, set the selected WEP key. 700If an 701.Ar index 702is not given, key 1 is set. 703A WEP key will be either 5 or 13 704characters (40 or 104 bits) depending of the local network and the 705capabilities of the adaptor. 706It may be specified either as a plain 707string or as a string of hexadecimal digits proceeded by 708.Ql 0x . 709For maximum portability, hex keys are recommended; 710the mapping of text keys to WEP encryption is usually driver-specific. 711In particular, the 712.Tn Windows 713drivers do this mapping differently to 714.Fx . 715A key may be cleared by setting it to 716.Ql - . 717If WEP is supported then there are at least four keys. 718Some adaptors support more than four keys. 719If that is the case, then the first four keys 720(1-4) will be the standard temporary keys and any others will be adaptor 721specific keys such as permanent keys stored in NVRAM. 722.It Cm wep 723Another way of saying 724.Cm wepmode on . 725Included for 726.Bsx 727compatibility. 728.It Fl wep 729Another way of saying 730.Cm wepmode off . 731Included for 732.Bsx 733compatibility. 734.It Cm nwkey key 735Another way of saying: 736.Pp 737.Dq Li "wepmode on weptxkey 1 wepkey 1:key wepkey 2:- wepkey 3:- wepkey 4:-" . 738.Pp 739Included for 740.Nx 741compatibility. 742.It Cm nwkey Xo 743.Sm off 744.Ar n : k1 , k2 , k3 , k4 745.Sm on 746.Xc 747Another way of saying 748.Pp 749.Dq Li "wepmode on weptxkey n wepkey 1:k1 wepkey 2:k2 wepkey 3:k3 wepkey 4:k4" . 750.Pp 751Included for 752.Nx 753compatibility. 754.It Fl nwkey 755Another way of saying 756.Cm wepmode off . 757.Pp 758Included for 759.Nx 760compatibility. 761.El 762.Pp 763The 764.Nm 765utility displays the current configuration for a network interface 766when no optional parameters are supplied. 767If a protocol family is specified, 768.Nm 769will report only the details specific to that protocol family. 770.Pp 771If the driver does supports the media selection system, the supported 772media list will be included in the output. 773.Pp 774If the 775.Fl m 776flag is passed before an interface name, 777.Nm 778will display the capability list and all 779of the supported media for the specified interface. 780If 781.Fl L 782flag is supplied, address lifetime is displayed for IPv6 addresses, 783as time offset string. 784.Pp 785Optionally, the 786.Fl a 787flag may be used instead of an interface name. 788This flag instructs 789.Nm 790to display information about all interfaces in the system. 791The 792.Fl d 793flag limits this to interfaces that are down, and 794.Fl u 795limits this to interfaces that are up. 796When no arguments are given, 797.Fl a 798is implied. 799.Pp 800The 801.Fl l 802flag may be used to list all available interfaces on the system, with 803no other additional information. 804Use of this flag is mutually exclusive 805with all other flags and commands, except for 806.Fl d 807(only list interfaces that are down) 808and 809.Fl u 810(only list interfaces that are up). 811.Pp 812The 813.Fl C 814flag may be used to list all of the interface cloners available on 815the system, with no additional information. 816Use of this flag is mutually exclusive with all other flags and commands. 817.Pp 818Only the super-user may modify the configuration of a network interface. 819.Sh NOTES 820The media selection system is relatively new and only some drivers support 821it (or have need for it). 822.Sh DIAGNOSTICS 823Messages indicating the specified interface does not exist, the 824requested address is unknown, or the user is not privileged and 825tried to alter an interface's configuration. 826.Sh BUGS 827Basic IPv6 node operation requires a link-local address on each 828interface configured for IPv6. 829Normally, such an address is automatically configured by the 830kernel on each interface added to the system; this behaviour may 831be disabled by setting the sysctl MIB variable 832.Va net.inet6.ip6.auto_linklocal 833to 0. 834.Pp 835If you delete such an address using 836.Nm , 837the kernel may act very oddly. 838Do this at your own risk. 839.Sh SEE ALSO 840.Xr netstat 1 , 841.Xr netintro 4 , 842.Xr vlan 4 , 843.\" .Xr eon 5 , 844.Xr rc 8 , 845.Xr routed 8 , 846.Xr sysctl 8 847.Sh HISTORY 848The 849.Nm 850utility appeared in 851.Bx 4.2 . 852