NAME
ifconfig - configure network interface parameters

SYNOPSIS
/usr/etc/ifconfig interface address_family
[ address [ dest_address ] ] [ parameters ]
/usr/etc/ifconfig interface [ protocol_family ]

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 or other operating parameters. The interface
parameter is a string of the form "name unit", e.g. "ie0".

Since an interface may receive transmissions in differing
protocols, each of which may require separate naming schemes, it is
necessary to specify the address_family, which may change the
interpretation of the remaining parameters. The address families
currently supported are "inet" and "ns".

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". For
the Xerox Network Systems family, addresses are net:a.b.c.d.e.f,
where net is the assigned network number (in decimal), and each of
the six bytes of the host number, a through f, are specified in
hexadecimal. The host number may be omitted on 10Mb/s Ethernet
interfaces, which use the hardware physical address, and on
interfaces other than the first.

The following parameters may be set with ifconfig:

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.

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.

trailers Request 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. On networks
that support the Address Resolution Protocol (see
arp(4); currently, only 10 Mb/s Ethernet), this flag
indicates that the system should request that other
systems use trailers when sending to this host.
Similarly, trailer encapsulations will be sent to
other hosts that have made such requests. Currently
used by Internet protocols only.

-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.

metric n 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.

debug Enable driver dependent debugging code; usually,
this turns on extra console error logging.

-debug Disable driver dependent debugging code.

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.

dest_address Specify the address of the correspondent on the
other end of a point to point link.

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 1’s.

old_broadcast (Inet only) Specifies an old-style broadcast address
with the host part of all 0’s; i.e. the result of
and’ing the interface address with the network mask.

ipdst (NS only) This is used to specify an Internet host
who is willing to receive ip packets encapsulating
NS packets bound for a remote network. In this
case, an apparent point to point link is
constructed, and the address specified will be taken
as the NS address and network of the destinee.

status Display the status of the network interface after
making all specified configuration changes.

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.

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

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