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.\" $FreeBSD$ 30.\" 31.Dd July 26, 2004 32.Dt IFCONFIG 8 33.Os 34.Sh NAME 35.Nm ifconfig 36.Nd configure network interface parameters 37.Sh SYNOPSIS 38.Nm 39.Op Fl L 40.Op Fl m 41.Ar interface 42.Op Cm create 43.Op Ar address_family 44.Oo 45.Ar address 46.Op Ar dest_address 47.Oc 48.Op Ar parameters 49.Nm 50.Ar interface 51.Cm destroy 52.Nm 53.Fl a 54.Op Fl L 55.Op Fl d 56.Op Fl m 57.Op Fl u 58.Op Ar address_family 59.Nm 60.Fl l 61.Op Fl d 62.Op Fl u 63.Op Ar address_family 64.Nm 65.Op Fl L 66.Op Fl d 67.Op Fl m 68.Op Fl u 69.Op Fl C 70.Sh DESCRIPTION 71The 72.Nm 73utility is used to assign an address 74to a network interface and/or configure 75network interface parameters. 76The 77.Nm 78utility must be used at boot time to define the network address 79of each interface present on a machine; it may also be used at 80a later time to redefine an interface's address 81or other operating parameters. 82.Pp 83The following options are available: 84.Bl -tag -width indent 85.It Ar address 86For the 87.Tn DARPA Ns -Internet 88family, 89the address is either a host name present in the host name data 90base, 91.Xr hosts 5 , 92or a 93.Tn DARPA 94Internet address expressed in the Internet standard 95.Dq dot notation . 96.Pp 97It is also possible to use the CIDR notation (also known as the 98slash notation) to include the netmask. 99That is, one can specify an address like 100.Li 192.168.0.1/16 . 101.Pp 102For 103.Dq inet6 104family, it is also possible to specify the prefix length using the slash 105notation, like 106.Li ::1/128 . 107See the 108.Cm prefixlen 109parameter below for more information. 110.\" For the Xerox Network Systems(tm) family, 111.\" addresses are 112.\" .Ar net:a.b.c.d.e.f , 113.\" where 114.\" .Ar net 115.\" is the assigned network number (in decimal), 116.\" and each of the six bytes of the host number, 117.\" .Ar a 118.\" through 119.\" .Ar f , 120.\" are specified in hexadecimal. 121.\" The host number may be omitted on IEEE 802 protocol 122.\" (Ethernet, FDDI, and Token Ring) interfaces, 123.\" which use the hardware physical address, 124.\" and on interfaces other than the first. 125.\" For the 126.\" .Tn ISO 127.\" family, addresses are specified as a long hexadecimal string, 128.\" as in the Xerox family. 129.\" However, two consecutive dots imply a zero 130.\" byte, and the dots are optional, if the user wishes to (carefully) 131.\" count out long strings of digits in network byte order. 132.Pp 133The link-level 134.Pq Dq link 135address 136is specified as a series of colon-separated hex digits. 137This can be used to 138e.g.\& set a new MAC address on an ethernet interface, though the 139mechanism used is not ethernet-specific. 140If the interface is already 141up when this option is used, it will be briefly brought down and 142then brought back up again in order to ensure that the receive 143filter in the underlying ethernet hardware is properly reprogrammed. 144.It Ar address_family 145Specify the 146address family 147which affects interpretation of the remaining parameters. 148Since an interface can receive transmissions in differing protocols 149with different naming schemes, specifying the address family is recommended. 150The address or protocol families currently 151supported are 152.Dq inet , 153.Dq inet6 , 154.Dq atalk , 155.Dq ipx , 156.\" .Dq iso , 157and 158.Dq link . 159.\" and 160.\" .Dq ns . 161The default is 162.Dq inet . 163.Dq ether 164and 165.Dq lladdr 166are synonyms for 167.Dq link . 168.It Ar dest_address 169Specify the address of the correspondent on the other end 170of a point to point link. 171.It Ar interface 172This 173parameter is a string of the form 174.Dq name unit , 175for example, 176.Dq Li ed0 . 177.El 178.Pp 179The following parameters may be set with 180.Nm : 181.Bl -tag -width indent 182.It Cm add 183Another name for the 184.Cm alias 185parameter. 186Introduced for compatibility 187with 188.Bsx . 189.It Cm alias 190Establish an additional network address for this interface. 191This is sometimes useful when changing network numbers, and 192one wishes to accept packets addressed to the old interface. 193If the address is on the same subnet as the first network address 194for this interface, a non-conflicting netmask must be given. 195Usually 196.Li 0xffffffff 197is most appropriate. 198.It Fl alias 199Remove the network address specified. 200This would be used if you incorrectly specified an alias, or it 201was no longer needed. 202If you have incorrectly set an NS address having the side effect 203of specifying the host portion, removing all NS addresses will 204allow you to respecify the host portion. 205.It Cm anycast 206(Inet6 only.) 207Specify that the address configured is an anycast address. 208Based on the current specification, 209only routers may configure anycast addresses. 210Anycast address will not be used as source address of any of outgoing 211IPv6 packets. 212.It Cm arp 213Enable the use of the Address Resolution Protocol 214.Pq Xr arp 4 215in mapping 216between network level addresses and link level addresses (default). 217This is currently implemented for mapping between 218.Tn DARPA 219Internet 220addresses and 221.Tn IEEE 222802 48-bit MAC addresses (Ethernet, FDDI, and Token Ring addresses). 223.It Fl arp 224Disable the use of the Address Resolution Protocol 225.Pq Xr arp 4 . 226.It Cm staticarp 227If the Address Resolution Protocol is enabled, 228the host will only reply to requests for its addresses, 229and will never send any requests. 230.It Fl staticarp 231If the Address Resolution Protocol is enabled, 232the host will perform normally, 233sending out requests and listening for replies. 234.It Cm broadcast 235(Inet only.) 236Specify the address to use to represent broadcasts to the 237network. 238The default broadcast address is the address with a host part of all 1's. 239.It Cm debug 240Enable driver dependent debugging code; usually, this turns on 241extra console error logging. 242.It Fl debug 243Disable driver dependent debugging code. 244.It Cm promisc 245Put interface into permanently promiscuous mode. 246.It Fl promisc 247Disable permanently promiscuous mode. 248.It Cm delete 249Another name for the 250.Fl alias 251parameter. 252.It Cm down 253Mark an interface 254.Dq down . 255When an interface is marked 256.Dq down , 257the system will not attempt to 258transmit messages through that interface. 259If possible, the interface will be reset to disable reception as well. 260This action does not automatically disable routes using the interface. 261.It Cm eui64 262(Inet6 only.) 263Fill interface index 264(lowermost 64bit of an IPv6 address) 265automatically. 266.It Cm ipdst 267This is used to specify an Internet host who is willing to receive 268IP packets encapsulating IPX packets bound for a remote network. 269An apparent point to point link is constructed, and 270the address specified will be taken as the IPX address and network 271of the destination. 272.It Cm maclabel Ar label 273If Mandatory Access Control support is enabled in the kernel, 274set the MAC label to 275.Ar label . 276.\" (see 277.\" .Xr maclabel 7 ) . 278.It Cm media Ar type 279If the driver supports the media selection system, set the media type 280of the interface to 281.Ar type . 282Some interfaces support the mutually exclusive use of one of several 283different physical media connectors. 284For example, a 10Mb/s Ethernet 285interface might support the use of either 286.Tn AUI 287or twisted pair connectors. 288Setting the media type to 289.Dq Li 10base5/AUI 290would change the currently active connector to the AUI port. 291Setting it to 292.Dq Li 10baseT/UTP 293would activate twisted pair. 294Refer to the interfaces' driver 295specific documentation or man page for a complete list of the 296available types. 297.It Cm mediaopt Ar opts 298If the driver supports the media selection system, set the specified 299media options on the interface. 300The 301.Ar opts 302argument 303is a comma delimited list of options to apply to the interface. 304Refer to the interfaces' driver specific man page for a complete 305list of available options. 306.It Fl mediaopt Ar opts 307If the driver supports the media selection system, disable the 308specified media options on the interface. 309.It Cm mode Ar mode 310If the driver supports the media selection system, set the specified 311operating mode on the interface to 312.Ar mode . 313For IEEE 802.11 wireless interfaces that support multiple operating modes 314this directive is used to select between 802.11a 315.Pq Dq Li 11a , 316802.11b 317.Pq Dq Li 11b , 318and 802.11g 319.Pq Dq Li 11g 320operating modes. 321.It Cm name Ar name 322Set the interface name to 323.Ar name . 324.It Cm rxcsum , txcsum 325If the driver supports user-configurable checksum offloading, 326enable receive (or transmit) checksum offloading on the interface. 327Some drivers may not be able to enable these flags independently 328of each other, so setting one may also set the other. 329The driver will offload as much checksum work as it can reliably 330support, the exact level of offloading varies between drivers. 331.It Fl rxcsum , Fl txcsum 332If the driver supports user-configurable checksum offloading, 333disable receive (or transmit) checksum offloading on the interface. 334These settings may not always be independent of each other. 335.It Cm polling 336If the driver has user-configurable 337.Xr polling 4 338support, select the polling mode on the interface. 339.It Fl polling 340If the driver has user-configurable 341.Xr polling 4 342support, select the interrupt mode on the interface. 343.It Cm tunnel Ar src_addr dest_addr 344(IP tunnel devices only.) 345Configure the physical source and destination address for IP tunnel 346interfaces 347.Pq Xr gif 4 . 348The arguments 349.Ar src_addr 350and 351.Ar dest_addr 352are interpreted as the outer source/destination for the encapsulating 353IPv4/IPv6 header. 354.It Cm deletetunnel 355Unconfigure the physical source and destination address for IP tunnel 356interfaces previously configured with 357.Cm tunnel . 358.It Cm create 359Create the specified network pseudo-device. 360If the interface is given without a unit number, try to create a new 361device with an arbitrary unit number. 362If creation of an arbitrary device is successful, the new device name is 363printed to standard output unless the interface is renamed or destroyed 364in the same 365.Nm 366invocation. 367.It Cm destroy 368Destroy the specified network pseudo-device. 369.It Cm plumb 370Another name for the 371.Cm create 372parameter. 373Included for 374.Tn Solaris 375compatibility. 376.It Cm unplumb 377Another name for the 378.Cm destroy 379parameter. 380Included for 381.Tn Solaris 382compatibility. 383.It Cm vlan Ar vlan_tag 384If the interface is a 385.Xr vlan 4 386pseudo interface, set the VLAN tag value 387to 388.Ar vlan_tag . 389This value is a 16-bit number which is used to create an 802.1Q 390VLAN header for packets sent from the 391.Xr vlan 4 392interface. 393Note that 394.Cm vlan 395and 396.Cm vlandev 397must both be set at the same time. 398.It Cm vlandev Ar iface 399If the interface is a 400.Xr vlan 4 401pseudo device, associate physical interface 402.Ar iface 403with it. 404Packets transmitted through the 405.Xr vlan 4 406interface will be 407diverted to the specified physical interface 408.Ar iface 409with 802.1Q VLAN encapsulation. 410Packets with 802.1Q encapsulation received 411by the parent interface with the correct VLAN tag will be diverted to 412the associated 413.Xr vlan 4 414pseudo-interface. 415The 416.Xr vlan 4 417interface is assigned a 418copy of the parent interface's flags and the parent's ethernet address. 419The 420.Cm vlandev 421and 422.Cm vlan 423must both be set at the same time. 424If the 425.Xr vlan 4 426interface already has 427a physical interface associated with it, this command will fail. 428To 429change the association to another physical interface, the existing 430association must be cleared first. 431.Pp 432Note: if the hardware tagging capability 433is set on the parent interface, the 434.Xr vlan 4 435pseudo 436interface's behavior changes: 437the 438.Xr vlan 4 439interface recognizes that the 440parent interface supports insertion and extraction of VLAN tags on its 441own (usually in firmware) and that it should pass packets to and from 442the parent unaltered. 443.It Fl vlandev Ar iface 444If the driver is a 445.Xr vlan 4 446pseudo device, disassociate the physical interface 447.Ar iface 448from it. 449This breaks the link between the 450.Xr vlan 4 451interface and its parent, 452clears its VLAN tag, flags and its link address and shuts the interface down. 453.It Cm vlanmtu , vlanhwtag 454If the driver offers user-configurable VLAN support, enable 455reception of extended frames or tag processing in hardware, 456respectively. 457Note that this must be issued on a physical interface associated with 458.Xr vlan 4 , 459not on a 460.Xr vlan 4 461interface itself. 462.It Fl vlanmtu , Fl vlanhwtag 463If the driver offers user-configurable VLAN support, disable 464reception of extended frames or tag processing in hardware, 465respectively. 466.It Cm metric Ar n 467Set the routing metric of the interface to 468.Ar n , 469default 0. 470The routing metric is used by the routing protocol 471.Pq Xr routed 8 . 472Higher metrics have the effect of making a route 473less favorable; metrics are counted as addition hops 474to the destination network or host. 475.It Cm mtu Ar n 476Set the maximum transmission unit of the interface to 477.Ar n , 478default is interface specific. 479The MTU is used to limit the size of packets that are transmitted on an 480interface. 481Not all interfaces support setting the MTU, and some interfaces have 482range restrictions. 483.It Cm netmask Ar mask 484.\" (Inet and ISO.) 485(Inet only.) 486Specify how much of the address to reserve for subdividing 487networks into sub-networks. 488The mask includes the network part of the local address 489and the subnet part, which is taken from the host field of the address. 490The mask can be specified as a single hexadecimal number 491with a leading 492.Ql 0x , 493with a dot-notation Internet address, 494or with a pseudo-network name listed in the network table 495.Xr networks 5 . 496The mask contains 1's for the bit positions in the 32-bit address 497which are to be used for the network and subnet parts, 498and 0's for the host part. 499The mask should contain at least the standard network portion, 500and the subnet field should be contiguous with the network 501portion. 502.Pp 503The netmask can also be specified in CIDR notation after the address. 504See the 505.Ar address 506option above for more information. 507.It Cm prefixlen Ar len 508(Inet6 only.) 509Specify that 510.Ar len 511bits are reserved for subdividing networks into sub-networks. 512The 513.Ar len 514must be integer, and for syntactical reason it must be between 0 to 128. 515It is almost always 64 under the current IPv6 assignment rule. 516If the parameter is omitted, 64 is used. 517.Pp 518The prefix can also be specified using the slash notation after the address. 519See the 520.Ar address 521option above for more information. 522.\" see 523.\" Xr eon 5 . 524.\" .It Cm nsellength Ar n 525.\" .Pf ( Tn ISO 526.\" only) 527.\" This specifies a trailing number of bytes for a received 528.\" .Tn NSAP 529.\" used for local identification, the remaining leading part of which is 530.\" taken to be the 531.\" .Tn NET 532.\" (Network Entity Title). 533.\" The default value is 1, which is conformant to US 534.\" .Tn GOSIP . 535.\" When an ISO address is set in an ifconfig command, 536.\" it is really the 537.\" .Tn NSAP 538.\" which is being specified. 539.\" For example, in 540.\" .Tn US GOSIP , 541.\" 20 hex digits should be 542.\" specified in the 543.\" .Tn ISO NSAP 544.\" to be assigned to the interface. 545.\" There is some evidence that a number different from 1 may be useful 546.\" for 547.\" .Tn AFI 548.\" 37 type addresses. 549.It Cm range Ar netrange 550Under appletalk, set the interface to respond to a 551.Ar netrange 552of the form 553.Ar startnet Ns - Ns Ar endnet . 554Appletalk uses this scheme instead of 555netmasks though 556.Fx 557implements it internally as a set of netmasks. 558.It Cm remove 559Another name for the 560.Fl alias 561parameter. 562Introduced for compatibility 563with 564.Bsx . 565.It Cm phase 566The argument following this specifies the version (phase) of the 567Appletalk network attached to the interface. 568Values of 1 or 2 are permitted. 569.Sm off 570.It Cm link Op Cm 0 No - Cm 2 571.Sm on 572Enable special processing of the link level of the interface. 573These three options are interface specific in actual effect, however, 574they are in general used to select special modes of operation. 575An example 576of this is to enable SLIP compression, or to select the connector type 577for some Ethernet cards. 578Refer to the man page for the specific driver 579for more information. 580.Sm off 581.It Fl link Op Cm 0 No - Cm 2 582.Sm on 583Disable special processing at the link level with the specified interface. 584.It Cm monitor 585Put the interface in monitor mode. 586No packets are transmitted, and received packets are discarded after 587.Xr bpf 4 588processing. 589.It Fl monitor 590Take the interface out of monitor mode. 591.It Cm up 592Mark an interface 593.Dq up . 594This may be used to enable an interface after an 595.Dq Nm Cm down . 596It happens automatically when setting the first address on an interface. 597If the interface was reset when previously marked down, 598the hardware will be re-initialized. 599.It Cm ssid Ar ssid 600For IEEE 802.11 wireless interfaces, set the desired Service Set 601Identifier (aka network name). 602The SSID is a string up to 32 characters 603in length and may be specified as either a normal string or in 604hexadecimal when proceeded by 605.Ql 0x . 606Additionally, the SSID may be cleared by setting it to 607.Ql - . 608.It Cm nwid Ar ssid 609Another name for the 610.Cm ssid 611parameter. 612Included for 613.Nx 614compatibility. 615.It Cm stationname Ar name 616For IEEE 802.11 wireless interfaces, set the name of this station. 617It appears that the station name is not really part of the IEEE 802.11 618protocol though all interfaces seem to support it. 619As such it only 620seems to be meaningful to identical or virtually identical equipment. 621Setting the station name is identical in syntax to setting the SSID. 622.It Cm station Ar name 623Another name for the 624.Cm stationname 625parameter. 626Included for 627.Bsx 628compatibility. 629.It Cm channel Ar number 630For IEEE 802.11 wireless interfaces, set the desired channel. 631Channels range from 1 to 14, but the exact selection available 632depends on the region your adaptor was manufactured for. 633Setting 634the channel to 0 will give you the default for your adaptor. 635Many 636adaptors ignore this setting unless you are in ad-hoc mode. 637.It Cm authmode Ar mode 638For IEEE 802.11 wireless interfaces, set the desired authentication mode 639in infrastructure mode. 640Not all adaptors support all modes. 641The set of 642valid modes is 643.Dq Li none , 644.Dq Li open , 645and 646.Dq Li shared . 647Modes are case insensitive. 648.It Cm powersave 649For IEEE 802.11 wireless interfaces, enable powersave mode. 650.It Fl powersave 651For IEEE 802.11 wireless interfaces, disable powersave mode. 652.It Cm powersavesleep Ar sleep 653For IEEE 802.11 wireless interfaces, set the desired max powersave sleep 654time in milliseconds. 655.It Cm protmode Ar technique 656For IEEE 802.11 wireless interfaces operating in 11g, use the specified 657.Ar technique 658for protecting OFDM frames in a mixed 11b/11g network. 659The set of valid techniques is 660.Dq Li off , 661.Dq Li cts 662(CTS to self), 663and 664.Dq Li rtscts 665(RTS/CTS). 666Technique names are case insensitive. 667.It Cm rtsthreshold Ar length 668For IEEE 802.11 wireless interfaces, set the threshold for which 669transmitted frames are preceded by transmission of an 670RTS 671control frame. 672The 673.Ar length 674argument 675is the frame size in bytes and must be in the range 1 to 2312. 676Not all adaptors support setting the RTS threshold. 677.It Cm txpower Ar power 678For IEEE 802.11 wireless interfaces, set the power used to transmit frames. 679The 680.Ar power 681argument 682is a unitless value in the range 0 to 100 that is interpreted 683by drivers to derive a device-specific value. 684Out of range values are truncated. 685Typically only a few discreet power settings are available and 686the driver will use the setting closest to the specified value. 687Not all adaptors support changing the transmit power. 688.It Cm wepmode Ar mode 689For IEEE 802.11 wireless interfaces, set the desired WEP mode. 690Not all adaptors support all modes. 691The set of valid modes is 692.Dq Li off , 693.Dq Li on , 694and 695.Dq Li mixed . 696The 697.Dq Li mixed 698mode explicitly tells the adaptor to allow association with access 699points which allow both encrypted and unencrypted traffic. 700On these adaptors, 701.Dq Li on 702means that the access point must only allow encrypted connections. 703On other adaptors, 704.Dq Li on 705is generally another name for 706.Dq Li mixed . 707Modes are case insensitive. 708.It Cm weptxkey Ar index 709For IEEE 802.11 wireless interfaces, set the WEP key to be used for 710transmission. 711.It Cm wepkey Ar key Ns | Ns Ar index : Ns Ar key 712For IEEE 802.11 wireless interfaces, set the selected WEP key. 713If an 714.Ar index 715is not given, key 1 is set. 716A WEP key will be either 5 or 13 717characters (40 or 104 bits) depending of the local network and the 718capabilities of the adaptor. 719It may be specified either as a plain 720string or as a string of hexadecimal digits proceeded by 721.Ql 0x . 722For maximum portability, hex keys are recommended; 723the mapping of text keys to WEP encryption is usually driver-specific. 724In particular, the 725.Tn Windows 726drivers do this mapping differently to 727.Fx . 728A key may be cleared by setting it to 729.Ql - . 730If WEP is supported then there are at least four keys. 731Some adaptors support more than four keys. 732If that is the case, then the first four keys 733(1-4) will be the standard temporary keys and any others will be adaptor 734specific keys such as permanent keys stored in NVRAM. 735.It Cm wep 736Another way of saying 737.Cm wepmode on . 738Included for 739.Bsx 740compatibility. 741.It Fl wep 742Another way of saying 743.Cm wepmode off . 744Included for 745.Bsx 746compatibility. 747.It Cm nwkey key 748Another way of saying: 749.Pp 750.Dq Li "wepmode on weptxkey 1 wepkey 1:key wepkey 2:- wepkey 3:- wepkey 4:-" . 751.Pp 752Included for 753.Nx 754compatibility. 755.It Cm nwkey Xo 756.Sm off 757.Ar n : k1 , k2 , k3 , k4 758.Sm on 759.Xc 760Another way of saying 761.Pp 762.Dq Li "wepmode on weptxkey n wepkey 1:k1 wepkey 2:k2 wepkey 3:k3 wepkey 4:k4" . 763.Pp 764Included for 765.Nx 766compatibility. 767.It Fl nwkey 768Another way of saying 769.Cm wepmode off . 770.Pp 771Included for 772.Nx 773compatibility. 774.El 775.Pp 776The 777.Nm 778utility displays the current configuration for a network interface 779when no optional parameters are supplied. 780If a protocol family is specified, 781.Nm 782will report only the details specific to that protocol family. 783.Pp 784If the driver does supports the media selection system, the supported 785media list will be included in the output. 786.Pp 787If the 788.Fl m 789flag is passed before an interface name, 790.Nm 791will display the capability list and all 792of the supported media for the specified interface. 793If 794.Fl L 795flag is supplied, address lifetime is displayed for IPv6 addresses, 796as time offset string. 797.Pp 798Optionally, the 799.Fl a 800flag may be used instead of an interface name. 801This flag instructs 802.Nm 803to display information about all interfaces in the system. 804The 805.Fl d 806flag limits this to interfaces that are down, and 807.Fl u 808limits this to interfaces that are up. 809When no arguments are given, 810.Fl a 811is implied. 812.Pp 813The 814.Fl l 815flag may be used to list all available interfaces on the system, with 816no other additional information. 817Use of this flag is mutually exclusive 818with all other flags and commands, except for 819.Fl d 820(only list interfaces that are down) 821and 822.Fl u 823(only list interfaces that are up). 824.Pp 825The 826.Fl C 827flag may be used to list all of the interface cloners available on 828the system, with no additional information. 829Use of this flag is mutually exclusive with all other flags and commands. 830.Pp 831Only the super-user may modify the configuration of a network interface. 832.Sh NOTES 833The media selection system is relatively new and only some drivers support 834it (or have need for it). 835.Sh DIAGNOSTICS 836Messages indicating the specified interface does not exist, the 837requested address is unknown, or the user is not privileged and 838tried to alter an interface's configuration. 839.Sh BUGS 840Basic IPv6 node operation requires a link-local address on each 841interface configured for IPv6. 842Normally, such an address is automatically configured by the 843kernel on each interface added to the system; this behaviour may 844be disabled by setting the sysctl MIB variable 845.Va net.inet6.ip6.auto_linklocal 846to 0. 847.Pp 848If you delete such an address using 849.Nm , 850the kernel may act very oddly. 851Do this at your own risk. 852.Sh SEE ALSO 853.Xr netstat 1 , 854.Xr netintro 4 , 855.Xr vlan 4 , 856.\" .Xr eon 5 , 857.Xr rc 8 , 858.Xr routed 8 , 859.Xr sysctl 8 860.Sh HISTORY 861The 862.Nm 863utility appeared in 864.Bx 4.2 . 865