.\" $NetBSD: ifconfig.8,v 1.124 2022/11/25 08:41:05 knakahara Exp $ .\" .\" Copyright (c) 1983, 1991, 1993 .\" 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. 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 8.4 (Berkeley) 6/1/94 .\" .Dd November 25, 2022 .Dt IFCONFIG 8 .Os .Sh NAME .Nm ifconfig .Nd configure network interface parameters .Sh SYNOPSIS .Nm .Op Fl N .Ar interface address_family .Oo .Ar address .Op Ar dest_address .Oc .Op Ar parameters .Nm .Op Fl hLmNvz .Ar interface .Op Ar protocol_family .Nm .Fl a .Op Fl bdhLNmsuvz .Op Ar protocol_family .Nm .Fl l .Op Fl bdsu .Nm .Fl s .Ar interface .Nm .Fl w .Ar secs .Op Fl W Ar secs .Nm .Fl C .Sh DESCRIPTION .Nm is used to assign an address to a network interface and/or configure network interface parameters. .Nm 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 : .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 . .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 recommended. The address or protocol families currently supported are .Dq inet , .Dq inet6 , .Dq atalk , and .Dq link . .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 : .Bl -tag -width dest_addressxx .It Cm active This keyword applies when .Nm adds or modifies any link-layer address. It indicates that .Nm should .Dq activate the address. Activation makes an address the default source for transmissions on the interface. You may not delete the active address from an interface. You must activate some other address, first. .It Cm advbase Ar n If the driver is a .Xr carp 4 pseudo-device, set the base advertisement interval to .Ar n seconds. This ia an 8-bit number; the default value is 1 second. .It Cm advskew Ar n If the driver is a .Xr carp 4 pseudo-device, skew the advertisement interval by .Ar n . This is an 8-bit number; the default value is 0. .Pp Taken together the .Cm advbase indicate how frequently, in seconds, the host will advertise the fact that it considers itself the master of the virtual host. The formula is .Cm advbase + .Pf ( Cm advskew / 256). If the master does not advertise within three times this interval, this host will begin advertising as master. .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 Fl alias Remove the specified network address alias. .It Cm arp Enable the use of the Address Resolution Protocol in mapping between network level addresses and link level addresses .Pq default . This is currently implemented for mapping between .Tn DARPA Internet addresses and Ethernet addresses. .It Fl arp Disable the use of the Address Resolution Protocol. .It Cm anycast .Pq inet6 only Set the IPv6 anycast address bit. .It Fl anycast .Pq inet6 only Clear the IPv6 anycast address bit. .It Cm broadcast Ar mask .Pq 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 carpdev Ar iface If the driver is a .Xr carp 4 pseudo-device, attach it to .Ar iface . If not specified, the kernel will attempt to select an interface with a subnet matching that of the carp interface. .It Cm description Ar description , Cm descr Ar description Set a description of the interface. (0-63 characters) .It Cm -description , Cm -descr Clear the description of the interface. .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. .Cm delete does not work for IPv6 addresses. Use .Fl alias with explicit IPv6 address instead. .It Ar 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 media Ar type Set the media type of the interface to .Ar type . Some interfaces support the mutually exclusive use of one of several different physical media connectors. For example, a 10Mb/s Ethernet interface might support the use of either .Tn AUI or twisted pair connectors. Setting the media type to .Dq 10base5 or .Dq AUI would change the currently active connector to the AUI port. Setting it to .Dq 10baseT or .Dq UTP would activate twisted pair. Refer to the interfaces' driver specific man page for a complete list of the available types and the .Xr ifmedia 4 manual page for a list of media types. See the .Fl m flag below. .It Cm mediaopt Ar opts Set the specified media options on the interface. .Ar opts is a comma delimited list of options to apply to the interface. Refer to the interfaces' driver specific man page for a complete list of available options. Also see the .Xr ifmedia 4 manual page for a list of media options. .It Fl mediaopt Ar opts Disable the specified media options on the interface. .It Cm mode Ar mode If the driver supports the media selection system, set the specified operating mode on the interface to .Ar mode . For IEEE 802.11 wireless interfaces that support multiple operating modes this directive is used to select between 802.11a .Pq Dq 11a , 802.11b .Pq Dq 11b , and 802.11g .Pq Dq 11g operating modes. .It Cm instance Ar minst Set the media instance to .Ar minst . This is useful for devices which have multiple physical layer interfaces .Pq PHYs . Setting the instance on such devices may not be strictly required by the network interface driver as the driver may take care of this automatically; see the driver's manual page for more information. .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 mtu Ar n Set the maximum transmission unit of the interface to .Ar n . Most interfaces do not support this option. .It Cm netmask Ar mask .Pq inet and inet6 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. .Pp For INET and INET6 addresses, the netmask can also be given with slash-notation after the address .Pq e.g 192.168.17.3/24 . .\" see .\" Xr eon 5 . .It Cm state Ar state Explicitly force the .Xr carp 4 pseudo-device to enter this state. Valid states are .Ar init , .Ar backup , and .Ar master . .It Cm frag Ar threshold .Pq IEEE 802.11 devices only Configure the fragmentation threshold for IEEE 802.11-based wireless network interfaces. .It Cm rts Ar threshold .Pq IEEE 802.11 devices only Configure the RTS/CTS threshold for IEEE 802.11-based wireless network interfaces. This controls the number of bytes used for the RTS/CTS handshake boundary. The .Ar threshold can be any value between 0 and 2347. The default is 2347, which indicates the RTS/CTS mechanism should not be used. .It Cm ssid Ar id .Pq IEEE 802.11 devices only Configure the Service Set Identifier (aka the network name) for IEEE 802.11-based wireless network interfaces. The .Ar id can either be any text string up to 32 characters in length, or a series of up to 64 hexadecimal digits preceded by .Dq 0x . Setting .Ar id to the empty string allows the interface to connect to any available access point. .It Cm nwid Ar id Synonym for .Dq ssid . .It Cm hidessid .Pq IEEE 802.11 devices only When operating as an access point, do not broadcast the SSID in beacon frames or respond to probe request frames unless they are directed to the ap (i.e., they include the ap's SSID). By default, the SSID is included in beacon frames and undirected probe request frames are answered. .It Fl hidessid .Pq IEEE 802.11 devices only When operating as an access point, broadcast the SSID in beacon frames and answer and respond to undirected probe request frames (default). .It Cm nwkey Ar key .Pq IEEE 802.11 devices only Enable WEP encryption for IEEE 802.11-based wireless network interfaces with the .Ar key . The .Ar key can either be a string, a series of hexadecimal digits preceded by .Dq 0x , or a set of keys in the form .Ar n:k1,k2,k3,k4 , where .Ar n specifies which of keys will be used for all transmitted packets, and four keys, .Ar k1 through .Ar k4 , are configured as WEP keys. Note that the order must be match within same network if multiple keys are used. For IEEE 802.11 wireless network, the length of each key is restricted to 40 bits, i.e., 5-character string or 10 hexadecimal digits, while the WaveLAN/IEEE Gold cards accept the 104 bits .Pq 13 characters key. .It Cm nwkey Cm persist .Pq IEEE 802.11 devices only Enable WEP encryption for IEEE 802.11-based wireless network interfaces with the persistent key written in the network card. .It Cm nwkey Cm persist : Ns Ar key .Pq IEEE 802.11 devices only Write the .Ar key to the persistent memory of the network card, and enable WEP encryption for IEEE 802.11-based wireless network interfaces with the .Ar key . .It Fl nwkey .Pq IEEE 802.11 devices only Disable WEP encryption for IEEE 802.11-based wireless network interfaces. .It Cm apbridge .Pq IEEE 802.11 devices only When operating as an access point, pass packets between wireless clients directly (default). .It Fl apbridge .Pq IEEE 802.11 devices only When operating as an access point, pass packets through the system so that they can be forwarded using some other mechanism. Disabling the internal bridging is useful when traffic is to be processed with packet filtering. .It Cm pass Ar passphrase If the driver is a .Xr carp 4 pseudo-device, set the authentication key to .Ar passphrase . There is no passphrase by default .It Cm powersave .Pq IEEE 802.11 devices only Enable 802.11 power saving mode. .It Fl powersave .Pq IEEE 802.11 devices only Disable 802.11 power saving mode. .It Cm powersavesleep Ar duration .Pq IEEE 802.11 devices only Set the receiver sleep duration in milliseconds for 802.11 power saving mode. .It Cm bssid Ar bssid .Pq IEEE 802.11 devices only Set the desired BSSID for IEEE 802.11-based wireless network interfaces. .It Fl bssid .Pq IEEE 802.11 devices only Unset the desired BSSID for IEEE 802.11-based wireless network interfaces. The interface will automatically select a BSSID in this mode, which is the default. .It Cm chan Ar chan .Pq IEEE 802.11 devices only Select the channel .Pq radio frequency to be used for IEEE 802.11-based wireless network interfaces. .It Fl chan .Pq IEEE 802.11 devices only Unset the desired channel to be used for IEEE 802.11-based wireless network interfaces. It does not affect the channel to be created for IBSS or hostap mode. .It Cm list scan .Pq IEEE 802.11 devices only Display the access points and/or ad-hoc neighbors located in the vicinity. The .Fl v flag may be used to display long SSIDs. .Fl v also causes received information elements to be displayed symbolically. The interface must be up before any scanning operation. Only the super-user can use this command. .It Cm tunnel Ar src_addr Ns Oo Ar ,src_port Oc Ar dest_addr Ns Oo Ar ,dest_port Oc .Pq IP tunnel devices only Configure the physical source and destination address for IP tunnel interfaces, including .Xr gif 4 . The arguments .Ar src_addr and .Ar dest_addr are interpreted as the outer source/destination for the encapsulating IPv4/IPv6 header. .Pp On a .Xr gre 4 interface in UDP mode, the arguments .Ar src_port and .Ar dest_port are interpreted as the outer source/destination port for the encapsulating UDP header. .It Cm deletetunnel Unconfigure the physical source and destination address for IP tunnel interfaces previously configured with .Cm tunnel . .It Cm session Ar local_session Ar remote_session .Pq L2TPv3 devices only Configure local session id and remote session id for L2TPv3 interface. The length of session id is 4 bytes. .It Cm deletesession Unconfigure the local session id and remote session id for L2TPv3 interface previously configured with .Cm session . .It Cm cookie Ar local_cookie_length Ar local_cookie Ar remote_cookie_length Ar remote_cookie .Pq L2TPv3 devices only Configure local cookie and remote cookie for L2TPv3 interface. The cookie length must be 4 or 8 bytes. Generally, cookies are managed by daemon. So, this command would be used for test or debug only. .It Cm deletecookie Unconfigure the local cookie and remote cookie for L2TPv3 interface previously configured with .Cm cookie . .It Cm create Create the specified network pseudo-device. .It Cm destroy Destroy the specified network pseudo-device. .It Cm pltime Ar n .Pq inet6 only Set preferred lifetime for the address. .It Cm prefixlen Ar n .Pq inet and inet6 only Effect is similar to .Cm netmask . but you can specify by prefix length by digits. .It Cm deprecated .Pq inet6 only Set the IPv6 deprecated address bit. .It Fl deprecated .Pq inet6 only Clear the IPv6 deprecated address bit. .It Cm eui64 .Pq inet6 only Fill interface index .Pq lowermost 64bit of an IPv6 address automatically. .It Cm link[0-2] Enable special processing of the link level of the interface. These three options are interface specific in actual effect, however, they are in general used to select special modes of operation. An example of this is to enable SLIP compression, or to select the connector type for some Ethernet cards. Refer to the man page for the specific driver for more information. .It Fl link[0-2] Disable special processing at the link level with the specified interface. .It Cm linkstr Ar str Set a link-level string parameter for the interface. This functionality varies from interface to interface. Refer to the man page for the specific driver for more information. .It Fl linkstr Remove an interface link-level string parameter. .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. .It Cm vhid Ar n If the driver is a .Xr carp 4 pseudo-device, set the virtual host ID to .Ar n . Acceptable values are 1 to 255. .It Cm vlan Ar vid If the interface is a .Xr vlan 4 pseudo-interface, set the VLAN identifier to .Ar vid . These are the first 12 bits (0-4095) from a 16-bit integer used to create an 802.1Q VLAN header for packets sent from the .Xr vlan 4 interface. Note that .Cm vlan and .Cm vlanif must be set at the same time. .It Cm vlanif Ar iface If the interface is a .Xr vlan 4 pseudo-interface, associate the physical interface .Ar iface with it. Packets transmitted through the .Xr vlan 4 interface will be diverted to the specified physical interface .Ar iface with 802.1Q VLAN encapsulation. Packets with 802.1Q encapsulation received by the physical interface with the correct VLAN tag will be diverted to the associated .Xr vlan 4 pseudo-interface. The VLAN interface is assigned a copy of the physical interface's flags and .Tn Ethernet address. If the .Xr vlan 4 interface already has a physical interface associated with it, this command will fail. To change the association to another physical interface, the existing association must be cleared first. Note that .Cm vlanif and .Cm vlan must be set at the same time. .It Cm -vlanif Ar iface Dissociate .Ar iface from the .Xr vlan 4 interface. .It Cm agrport Ar iface Add .Ar iface to the .Xr agr 4 interface. .It Cm -agrport Ar iface Remove .Ar iface from the .Xr agr 4 interface. .It Cm eee Enable IEEE 802.3az Energy Efficiency Ethernet function. .It Cm -eee Disable IEEE 802.3az Energy Efficiency Ethernet function. .It Cm vltime Ar n .Pq inet6 only Set valid lifetime for the address. .It Cm ip4csum Shorthand of .Dq ip4csum-tx ip4csum-rx .It Cm -ip4csum Shorthand of .Dq -ip4csum-tx -ip4csum-rx .It Cm tcp4csum Shorthand of .Dq tcp4csum-tx tcp4csum-rx .It Cm -tcp4csum Shorthand of .Dq -tcp4csum-tx -tcp4csum-rx .It Cm udp4csum Shorthand of .Dq udp4csum-tx udp4csum-rx .It Cm -udp4csum Shorthand of .Dq -udp4csum-tx -udp4csum-rx .It Cm tcp6csum Shorthand of .Dq tcp6csum-tx tcp6csum-rx .It Cm -tcp6csum Shorthand of .Dq -tcp6csum-tx -tcp6csum-rx .It Cm udp6csum Shorthand of .Dq udp6csum-tx udp6csum-rx .It Cm -udp6csum Shorthand of .Dq -udp6csum-tx -udp6csum-rx .It Cm ip4csum-tx Enable hardware-assisted IPv4 header checksums for the out-bound direction. .It Cm -ip4csum-tx Disable hardware-assisted IPv4 header checksums for the out-bound direction. .It Cm ip4csum-rx Enable hardware-assisted IPv4 header checksums for the in-bound direction. .It Cm -ip4csum-rx Disable hardware-assisted IPv4 header checksums for the in-bound direction. .It Cm tcp4csum-tx Enable hardware-assisted TCP/IPv4 checksums for the out-bound direction. .It Cm -tcp4csum-tx Disable hardware-assisted TCP/IPv4 checksums for the out-bound direction. .It Cm tcp4csum-rx Enable hardware-assisted TCP/IPv4 checksums for the in-bound direction. .It Cm -tcp4csum-rx Disable hardware-assisted TCP/IPv4 checksums for the in-bound direction. .It Cm udp4csum-tx Enable hardware-assisted UDP/IPv4 checksums for the out-bound direction. .It Cm -udp4csum-tx Disable hardware-assisted UDP/IPv4 checksums for the out-bound direction. .It Cm udp4csum-rx Enable hardware-assisted UDP/IPv4 checksums for the in-bound direction. .It Cm -udp4csum-rx Disable hardware-assisted UDP/IPv4 checksums for the in-bound direction. .It Cm tcp6csum-tx Enable hardware-assisted TCP/IPv6 checksums for the out-bound direction. .It Cm -tcp6csum-tx Disable hardware-assisted TCP/IPv6 checksums for the out-bound direction. .It Cm tcp6csum-rx Enable hardware-assisted TCP/IPv6 checksums for the in-bound direction. .It Cm -tcp6csum-rx Disable hardware-assisted TCP/IPv6 checksums for the in-bound direction. .It Cm udp6csum-tx Enable hardware-assisted UDP/IPv6 checksums for the out-bound direction. .It Cm -udp6csum-tx Disable hardware-assisted UDP/IPv6 checksums for the out-bound direction. .It Cm udp6csum-rx Enable hardware-assisted UDP/IPv6 checksums for the in-bound direction. .It Cm -udp6csum-rx Disable hardware-assisted UDP/IPv6 checksums for the in-bound direction. .It Cm tso4 Enable hardware-assisted TCP/IPv4 segmentation on interfaces that support it. .It Cm -tso4 Disable hardware-assisted TCP/IPv4 segmentation on interfaces that support it. .It Cm tso6 Enable hardware-assisted TCP/IPv6 segmentation on interfaces that support it. .It Cm -tso6 Disable hardware-assisted TCP/IPv6 segmentation on interfaces that support it. .It Cm vlan-hwfilter Enable hardware-assisted VLAN frame filter on interfaces that support it. .It Cm -vlan-hwfilter Disable hardware-assisted VLAN frame filter on interfaces that support it. .It Cm vlan-hwtagging Enable hardware-assisted VLAN tag insertion/removal on interfaces that support it. .It Cm -vlan-hwtagging Disable hardware-assisted VLAN tag insertion/removal on interfaces that support it. .It Cm maxupd Ar n If the driver is a .Xr pfsync 4 pseudo-device, indicate the maximum number of updates for a single state which can be collapsed into one. This is an 8-bit number; the default value is 128. .It Cm syncdev Ar iface If the driver is a .Xr pfsync 4 pseudo-device, use the specified interface to send and receive pfsync state synchronisation messages. .It Fl syncdev If the driver is a .Xr pfsync 4 pseudo-device, stop sending pfsync state synchronisation messages over the network. .It Cm syncpeer Ar peer_address If the driver is a .Xr pfsync 4 pseudo-device, make the pfsync link point-to-point rather than using multicast to broadcast the state synchronisation messages. The peer_address is the IP address of the other host taking part in the pfsync cluster. With this option, .Xr pfsync 4 traffic can be protected using .Xr ipsec 4 . .It Fl syncpeer If the driver is a .Xr pfsync 4 pseudo-device, broadcast the packets using multicast. .It Cm unnumbered Treat the interface as unnumbered. .It Cm -unnumbered Don't treat the interface as unnumbered. .El .Pp .Nm displays the current configuration for a network interface when no optional parameters are supplied. If a protocol family is specified, .Nm will report only the details specific to that protocol family. .Pp If the .Fl s flag is passed before an interface name, .Nm will attempt to query the interface for its media status. If the interface supports reporting media status, and it reports that it does not appear to be connected to a network, .Nm will exit with status of 1 .Pq false ; otherwise, it will exit with a zero .Pq true exit status. For interface drivers that do not support media status reporting. then if the link state is not reported to be up, .Nm will exit with a status of 1 .Pq false ; otherwise, it will exit with a zero .Pq true exit status. .Pp If the .Fl m flag is passed before an interface name, .Nm will display all of the supported media for the specified interface. If the .Fl L flag is supplied, address lifetime is displayed for IPv6 addresses, as time offset string. .Pp Optionally, the .Fl a flag may be used instead of an interface name. This flag instructs .Nm to display information about all interfaces in the system. This is also the default behaviour when no arguments are given to .Nm on the command line. When .Fl a is used, the output can be modified by adding more flags: .Fl d limits this to interfaces that are down, .Fl u limits this to interfaces that are up, .Fl b limits this to broadcast interfaces, and .Fl s omits interfaces which appear not to be connected to a network. .Pp The .Fl l flag may be used to list all available interfaces on the system, with no other additional information. Use of this flag is mutually exclusive with all other flags and commands, except for .Fl d .Pq only list interfaces that are down , .Fl u .Pq only list interfaces that are up , .Fl s .Pq only list interfaces that may be connected , .Fl b .Pq only list broadcast interfaces . .Pp The .Fl C flag may be used to list all of the interface cloners available on the system, with no additional information. Use of this flag is mutually exclusive with all other flags and commands. .Pp The .Fl v flag prints statistics on packets sent and received on the given interface. If .Fl h is used in conjunction with .Fl v , the byte statistics will be printed in "human-readable" format. The .Fl z flag is identical to the .Fl v flag except that it zeros the interface input and output statistics after printing them. .Pp The .Fl w flag may be used to wait .Ar seconds seconds for the .Cm tentative flag to be removed from all addresses. 0 seconds means to wait indefinitely until all addresses no longer have the .Cm tentative flag. The optional .Fl W flag may be used to wait .Ar seconds seconds during the above time for the detached flag to be removed from all addresses whose interface is marked ``up'' as well. The detached flag is set when the interface does not have a carrier. .Pp The .Fl N flag is just the opposite of the .Fl n flag in .Xr netstat 1 or in .Xr route 8 : it tells .Nm to try to resolve numbers to hostnames or to service names. The default .Nm behavior is to print numbers instead of names. .Pp Only the super-user may modify the configuration of a network interface. .Sh EXAMPLES Add a link-layer (MAC) address to an Ethernet: .Pp .Ic ifconfig sip0 link 00:11:22:33:44:55 .Pp Add and activate a link-layer (MAC) address: .Pp .Ic ifconfig sip0 link 00:11:22:33:44:55 active .Sh DIAGNOSTICS Messages indicating the specified interface does not exist, 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 agr 4 , .Xr carp 4 , .Xr ifmedia 4 , .Xr netintro 4 , .Xr pfsync 4 , .Xr vlan 4 , .Xr ifconfig.if 5 , .\" .Xr eon 5 , .Xr ifmcstat 8 , .Xr rc 8 , .Xr routed 8 .Sh BUGS Due to hardware limitations some of the capabilities cannot be turned on and off individually and need to be specified together. For example the .Xr ixg 4 driver can't enable separately tcp and udp, or the transmit and receive checksumming capabilities. Unfortunately the diagnostic messages in this case are lacking. .Sh HISTORY The .Nm command appeared in .Bx 4.2 .