IFCONFIG(8C)

NAME
ifconfig - configure network interface parameters

SYOPNSIS
/etc/ifconfig interface [ address ] [ parameters ]

DESCRIPTION
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. The interface parameter is a string of the form ``name unit'', e.g. ``se0'', while the address is either a host name present in the host name data base, hosts(5), or an address expressed in the Internet standard ``dot notation''.

The following parameters may be set with ifconfig:

up  Mark an interface ``up''.

down
    Mark an interface ``down''. When an interface is marked ``down'', the system will not attempt to transmit messages through that interface.

trailers
    Enable the use of a ``trailer'' link level encapsulation when sending (default). If a network interface supports trailers, the system will, when possible, encapsulate outgoing messages in a manner which minimizes the number of memory to memory copy operations performed by the receiver.

-trailers
    Disable the use of a ``trailer'' link level encapsulation.

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 10Mb/s Ethernet addresses.

-arp
    Disable the use of the Address Resolution Protocol. Not possible when mixing vendors on the same Ethernet cable.

netmask mask
    (Inet only) 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.

broadcast
    (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 0's.

mtu ddd
    Set the maximum transfer unit on this interface to ddd (a decimal number).

Ifconfig displays the current configuration for a network interface when no optional parameters are supplied.

Only the super-user may modify the configuration of a network interface.

DIAGNOSTICS
Messages indicating the specified interface does not exist, the requested address is unknown, the user is not privileged and tried to alter an interface's configuration.

SEE ALSO
netstat(1), intro(4N), rc(8)