String of the form name unit: for example, en0.

Since an interface may receive transmissions in differing protocols, each of which may require separate naming schemes, you can specify the address_family to change the interpretation of the remaining parameters. You may specify inet (for TCP/IP, the default), ax25 (AX.25 Packet Radio), ddp (Appletalk Phase 2), or ipx (Novell).

The following parameters may be set with ifconfig:

add address/prefixlength

Add an IPv6 address and prefix length.

address address

Assign the specified IP address to the interface.

allmulti/-allmulti

Enable/disable sending of incoming frames to the kernel's network layer.

arp/-arp

Enable/disable use of the Address Resolution Protocol in mapping between network-level addresses and link-level addresses.

broadcast [address]

(inet only) Specify address to use to represent broadcasts to the network. Default is the address with a host part of all ones (i.e., x.y.z.255 for a class C network).

debug/-debug

Enable/disable driver-dependent debugging code.

del address/prefixlength

Delete an IPv6 address and prefix length.

down

Mark an interface "down" (unresponsive).

hw class address

Set the interface's hardware class and address. class may be ether (Ethernet), ax25 (AX.25 Packet Radio), or ARCnet.

io_addr addr

I/O memory start address for device.

irq addr

Set the device's interrupt line.

metric n

Set routing metric of the interface to n. Default is 0.

mem_start addr

Shared memory start address for device.

media type

Set media type. Common values are 10base2, 10baseT, and AUI. If auto is specified, ifconfig will attempt to autosense the media type.

mtu n

Set the interface's Maximum Transfer Unit (MTU).

multicast

Set the multicast flag.

netmask mask

(inet only) Specify how much of the address to reserve for subdividing networks into subnetworks. 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 /etc/networks.

pointopoint/-pointopoint [address]

Enable/disable point-to-point interfacing, so that the connection between the two machines is dedicated.

promisc/-promisc

Enable/disable promiscuous mode. Promiscuous mode allows the device to receive all packets on the network.

txqueuelen n

Specify the transmit queue length.

tunnel addr

Create an IPv6-in-IPv4 (SIT) device, tunneling to IPv4 address addr.

up

Mark an interface "up" (ready to send and receive).

Each address is either a hostname present in the hostname database (/etc/hosts), or an Internet address expressed in the Internet standard dot notation.