ifconfig is used to assign an address to a network
  interface and/or configure network interface parameters.
  ifconfig must be used at boot time to define the
  network address of each interface present on a machine; it may also be used at
  a later time to redefine an interface's address or other operating parameters.
Available operands for ifconfig:
  - address
- For the DARPA-Internet family, the address is either a host name present
      in the host name data base,
      hosts(5), or a DARPA Internet
      address expressed in the Internet standard “dot
    notation”.
- address_family
- Specifies the 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 “inet”,
      “inet6”, “atalk”, and
    “link”.
- interface
- The interface parameter is a string of the form
      “name unit”, for example, “en0”
The following parameters may be set with
    ifconfig:
  - active
- This keyword applies when ifconfigadds or
      modifies any link-layer address. It indicates thatifconfigshould “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.
- advbasen
- If the driver is a carp(4)
      pseudo-device, set the base advertisement interval to
      n seconds. This ia an 8-bit number; the default
      value is 1 second.
- advskewn
- If the driver is a carp(4)
      pseudo-device, skew the advertisement interval by n.
      This is an 8-bit number; the default value is 0.
    Taken together the advbaseindicate
        how frequently, in seconds, the host will advertise the fact that it
        considers itself the master of the virtual host. The formula isadvbase+ (advskew/
        256). If the master does not advertise within three times this interval,
        this host will begin advertising as master.
 
- 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.
- -alias
- Remove the specified network address alias.
- arp
- Enable the use of the Address Resolution Protocol in mapping between
      network level addresses and link level addresses (default). This is
      currently implemented for mapping between DARPA Internet addresses and
      Ethernet addresses.
- -arp
- Disable the use of the Address Resolution Protocol.
- anycast
- (inet6 only) Set the IPv6 anycast address bit.
- -anycast
- (inet6 only) Clear the IPv6 anycast address bit.
- broadcastmask
- (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.
- carpdeviface
- If the driver is a carp(4)
      pseudo-device, attach it to iface. If not specified,
      the kernel will attempt to select an interface with a subnet matching that
      of the carp interface.
- descriptiondescription,- descrdescription
- Set a description of the interface. (0-63 characters)
- -description,- -descr
- Clear the description of the interface.
- debug
- Enable driver dependent debugging code; usually, this turns on extra
      console error logging.
- -debug
- Disable driver dependent debugging code.
- 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. deletedoes not work for IPv6
      addresses. Use-aliaswith explicit IPv6 address
      instead.
- dest_address
- Specify the address of the correspondent on the other end of a point to
      point link.
- 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.
- mediatype
- Set the media type of the interface to 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 AUI or twisted pair connectors. Setting the
      media type to “10base5” or “AUI” would change
      the currently active connector to the AUI port. Setting it to
      “10baseT” or “UTP” would activate twisted
      pair. Refer to the interfaces' driver specific man page for a complete
      list of the available types and the
      ifmedia(4) manual page for
      a list of media types. See the -mflag below.
- mediaoptopts
- Set the specified media options on the interface.
      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
      ifmedia(4) manual page for
      a list of media options.
- -mediaoptopts
- Disable the specified media options on the interface.
- modemode
- If the driver supports the media selection system, set the specified
      operating mode on the interface to mode. For IEEE
      802.11 wireless interfaces that support multiple operating modes this
      directive is used to select between 802.11a (“11a”), 802.11b
      (“11b”), and 802.11g (“11g”) operating
    modes.
- instanceminst
- Set the media instance to minst. This is useful for
      devices which have multiple physical layer interfaces (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.
- metricn
- Set the routing metric of the interface to n,
      default 0. The routing metric is used by the routing protocol
      (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.
- mtun
- Set the maximum transmission unit of the interface to
      n. Most interfaces do not support this option.
- netmaskmask
- (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
      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.
    For INET and INET6 addresses, the netmask can also be given
        with slash-notation after the address (e.g 192.168.17.3/24). 
- statestate
- Explicitly force the carp(4)
      pseudo-device to enter this state. Valid states are
      init, backup, and
      master.
- fragthreshold
- (IEEE 802.11 devices only) Configure the fragmentation threshold for IEEE
      802.11-based wireless network interfaces.
- rtsthreshold
- (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
      threshold can be any value between 0 and 2347. The
      default is 2347, which indicates the RTS/CTS mechanism should not be
    used.
- ssidid
- (IEEE 802.11 devices only) Configure the Service Set Identifier (aka the
      network name) for IEEE 802.11-based wireless network interfaces. The
      id can either be any text string up to 32 characters
      in length, or a series of up to 64 hexadecimal digits preceded by
      “0x”. Setting id to the empty string
      allows the interface to connect to any available access point.
- nwidid
- Synonym for “ssid”.
- hidessid
- (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.
- -hidessid
- (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).
- nwkeykey
- (IEEE 802.11 devices only) Enable WEP encryption for IEEE 802.11-based
      wireless network interfaces with the key. The
      key can either be a string, a series of hexadecimal
      digits preceded by “0x”, or a set of keys in the form
      n:k1,k2,k3,k4, where n
      specifies which of keys will be used for all transmitted packets, and four
      keys, k1 through 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 (13 characters) key.
- nwkey- persist
- (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.
- nwkey- persist:key
- (IEEE 802.11 devices only) Write the key to the
      persistent memory of the network card, and enable WEP encryption for IEEE
      802.11-based wireless network interfaces with the
      key.
- -nwkey
- (IEEE 802.11 devices only) Disable WEP encryption for IEEE 802.11-based
      wireless network interfaces.
- apbridge
- (IEEE 802.11 devices only) When operating as an access point, pass packets
      between wireless clients directly (default).
- -apbridge
- (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.
- passpassphrase
- If the driver is a carp(4)
      pseudo-device, set the authentication key to
      passphrase. There is no passphrase by default
- powersave
- (IEEE 802.11 devices only) Enable 802.11 power saving mode.
- -powersave
- (IEEE 802.11 devices only) Disable 802.11 power saving mode.
- powersavesleepduration
- (IEEE 802.11 devices only) Set the receiver sleep duration in milliseconds
      for 802.11 power saving mode.
- bssidbssid
- (IEEE 802.11 devices only) Set the desired BSSID for IEEE 802.11-based
      wireless network interfaces.
- -bssid
- (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.
- chanchan
- (IEEE 802.11 devices only) Select the channel (radio frequency) to be used
      for IEEE 802.11-based wireless network interfaces.
- -chan
- (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.
- list
    scan
- (IEEE 802.11 devices only) Display the access points and/or ad-hoc
      neighbors located in the vicinity. The -vflag may
      be used to display long SSIDs.-valso 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.
- tunnelsrc_addr[,src_port]
    dest_addr[,dest_port]
- (IP tunnel devices only) Configure the physical source and destination
      address for IP tunnel interfaces, including
      gif(4). The arguments
      src_addr and dest_addr are
      interpreted as the outer source/destination for the encapsulating
      IPv4/IPv6 header.
    On a gre(4)
        interface in UDP mode, the arguments src_port and
        dest_port are interpreted as the outer
        source/destination port for the encapsulating UDP header. 
- deletetunnel
- Unconfigure the physical source and destination address for IP tunnel
      interfaces previously configured with tunnel.
- sessionlocal_session
    remote_session
- (L2TPv3 devices only) Configure local session id and remote session id for
      L2TPv3 interface. The length of session id is 4 bytes.
- deletesession
- Unconfigure the local session id and remote session id for L2TPv3
      interface previously configured with session.
- cookielocal_cookie_length local_cookie
    remote_cookie_length
    remote_cookie
- (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.
- deletecookie
- Unconfigure the local cookie and remote cookie for L2TPv3 interface
      previously configured with cookie.
- create
- Create the specified network pseudo-device.
- destroy
- Destroy the specified network pseudo-device.
- pltimen
- (inet6 only) Set preferred lifetime for the address.
- prefixlenn
- (inet and inet6 only) Effect is similar to
      netmask. but you can specify by prefix length by
      digits.
- deprecated
- (inet6 only) Set the IPv6 deprecated address bit.
- -deprecated
- (inet6 only) Clear the IPv6 deprecated address bit.
- eui64
- (inet6 only) Fill interface index (lowermost 64bit of an IPv6 address)
      automatically.
- 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.
- -link[0-2]
- Disable special processing at the link level with the specified
    interface.
- linkstrstr
- 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.
- -linkstr
- Remove an interface link-level string parameter.
- 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.
- vhidn
- If the driver is a carp(4)
      pseudo-device, set the virtual host ID to n.
      Acceptable values are 1 to 255.
- vlanvid
- If the interface is a vlan(4)
      pseudo-interface, set the VLAN identifier to 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
      vlan(4) interface. Note that
      vlanandvlanifmust be
      set at the same time.
- vlanififace
- If the interface is a vlan(4)
      pseudo-interface, associate the physical interface
      iface with it. Packets transmitted through the
      vlan(4) interface will be
      diverted to the specified physical interface 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 vlan(4)
      pseudo-interface. The VLAN interface is assigned a copy of the physical
      interface's flags and Ethernet address. If the
      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 vlanifandvlanmust be set at the same time.
- -vlanififace
- Dissociate iface from the
      vlan(4) interface.
- agrportiface
- Add iface to the
      agr(4) interface.
- -agrportiface
- Remove iface from the
      agr(4) interface.
- vltimen
- (inet6 only) Set valid lifetime for the address.
- ip4csum
- Shorthand of “ip4csum-tx ip4csum-rx”
- -ip4csum
- Shorthand of “-ip4csum-tx -ip4csum-rx”
- tcp4csum
- Shorthand of “tcp4csum-tx tcp4csum-rx”
- -tcp4csum
- Shorthand of “-tcp4csum-tx -tcp4csum-rx”
- udp4csum
- Shorthand of “udp4csum-tx udp4csum-rx”
- -udp4csum
- Shorthand of “-udp4csum-tx -udp4csum-rx”
- tcp6csum
- Shorthand of “tcp6csum-tx tcp6csum-rx”
- -tcp6csum
- Shorthand of “-tcp6csum-tx -tcp6csum-rx”
- udp6csum
- Shorthand of “udp6csum-tx udp6csum-rx”
- -udp6csum
- Shorthand of “-udp6csum-tx -udp6csum-rx”
- ip4csum-tx
- Enable hardware-assisted IPv4 header checksums for the out-bound
      direction.
- -ip4csum-tx
- Disable hardware-assisted IPv4 header checksums for the out-bound
      direction.
- ip4csum-rx
- Enable hardware-assisted IPv4 header checksums for the in-bound
    direction.
- -ip4csum-rx
- Disable hardware-assisted IPv4 header checksums for the in-bound
      direction.
- tcp4csum-tx
- Enable hardware-assisted TCP/IPv4 checksums for the out-bound
    direction.
- -tcp4csum-tx
- Disable hardware-assisted TCP/IPv4 checksums for the out-bound
    direction.
- tcp4csum-rx
- Enable hardware-assisted TCP/IPv4 checksums for the in-bound
    direction.
- -tcp4csum-rx
- Disable hardware-assisted TCP/IPv4 checksums for the in-bound
    direction.
- udp4csum-tx
- Enable hardware-assisted UDP/IPv4 checksums for the out-bound
    direction.
- -udp4csum-tx
- Disable hardware-assisted UDP/IPv4 checksums for the out-bound
    direction.
- udp4csum-rx
- Enable hardware-assisted UDP/IPv4 checksums for the in-bound
    direction.
- -udp4csum-rx
- Disable hardware-assisted UDP/IPv4 checksums for the in-bound
    direction.
- tcp6csum-tx
- Enable hardware-assisted TCP/IPv6 checksums for the out-bound
    direction.
- -tcp6csum-tx
- Disable hardware-assisted TCP/IPv6 checksums for the out-bound
    direction.
- tcp6csum-rx
- Enable hardware-assisted TCP/IPv6 checksums for the in-bound
    direction.
- -tcp6csum-rx
- Disable hardware-assisted TCP/IPv6 checksums for the in-bound
    direction.
- udp6csum-tx
- Enable hardware-assisted UDP/IPv6 checksums for the out-bound
    direction.
- -udp6csum-tx
- Disable hardware-assisted UDP/IPv6 checksums for the out-bound
    direction.
- udp6csum-rx
- Enable hardware-assisted UDP/IPv6 checksums for the in-bound
    direction.
- -udp6csum-rx
- Disable hardware-assisted UDP/IPv6 checksums for the in-bound
    direction.
- tso4
- Enable hardware-assisted TCP/IPv4 segmentation on interfaces that support
      it.
- -tso4
- Disable hardware-assisted TCP/IPv4 segmentation on interfaces that support
      it.
- tso6
- Enable hardware-assisted TCP/IPv6 segmentation on interfaces that support
      it.
- -tso6
- Disable hardware-assisted TCP/IPv6 segmentation on interfaces that support
      it.
- vlan-hwtagging
- Enable hardware-assisted VLAN tag insertion/removal on interfaces that
      support it.
- -vlan-hwtagging
- Disable hardware-assisted VLAN tag insertion/removal on interfaces that
      support it.
- maxupdn
- If the driver is a 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.
- syncdeviface
- If the driver is a pfsync(4)
      pseudo-device, use the specified interface to send and receive pfsync
      state synchronisation messages.
- -syncdev
- If the driver is a pfsync(4)
      pseudo-device, stop sending pfsync state synchronisation messages over the
      network.
- syncpeerpeer_address
- If the driver is a 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,
      pfsync(4) traffic can be
      protected using
    ipsec(4).
- -syncpeer
- If the driver is a pfsync(4)
      pseudo-device, broadcast the packets using multicast.
ifconfig displays the current
    configuration for a network interface when no optional parameters are
    supplied. If a protocol family is specified,
    ifconfig will report only the details specific to
    that protocol family.
If the -s flag is passed before an
    interface name, ifconfig 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,
    ifconfig will exit with status of 1 (false);
    otherwise, it will exit with a zero (true) exit status. Not all interface
    drivers support media status reporting.
If the -m flag is passed before an
    interface name, ifconfig will display all of the
    supported media for the specified interface. If the
    -L flag is supplied, address lifetime is displayed
    for IPv6 addresses, as time offset string.
Optionally, the -a flag may be used
    instead of an interface name. This flag instructs
    ifconfig to display information about all interfaces
    in the system. This is also the default behaviour when no arguments are
    given to ifconfig on the command line. When
    -a is used, the output can be modified by adding
    more flags: -d limits this to interfaces that are
    down, -u limits this to interfaces that are up,
    -b limits this to broadcast interfaces, and
    -s omits interfaces which appear not to be connected
    to a network.
The -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 -d (only list interfaces that are down),
    -u (only list interfaces that are up),
    -s (only list interfaces that may be connected),
    -b (only list broadcast interfaces).
The -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.
The -v flag prints statistics on packets
    sent and received on the given interface. If -h is
    used in conjunction with -v, the byte statistics
    will be printed in "human-readable" format. The
    -z flag is identical to the
    -v flag except that it zeros the interface input and
    output statistics after printing them.
The -w flag may be used to wait
    seconds seconds for the
    tentative flag to be removed from all addresses. 0
    seconds means to wait indefinitely until all addresses no longer have the
    tentative flag. The optional
    -W flag may be used to wait
    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.
The -N flag is just the opposite of the
    -n flag in
    netstat(1) or in
    route(8): it tells
    ifconfig to try to resolve numbers to hostnames or
    to service names. The default ifconfig behavior is
    to print numbers instead of names.
Only the super-user may modify the configuration of a network
    interface.