ifconfig - configure network interface parameters
/sbin/ifconfig interface address_family [ address [ dest_address ] ] [ parameters ]
/sbin/ifconfig interface [ protocol_family ]
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. ``en0''.
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(tm) 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 sys-
tem will not attempt to transmit messages through that interface. If pos-
sible, 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(4P); cur-
rently, only 10 Mb/s Ethernet), this flag indicates that the system should
request that other systems use trailers when sending to this host. Simi-
larly, 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 net-
work level addresses and link level addresses (default). This is currently
implemented for mapping between DARPA Internet addresses and 10Mb/s Ether-
-arp Disable the use of the Address Resolution Protocol.
metric n Set the routing metric of the interface to n, default 0. The routing met-
ric 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 con-
sole error logging.
-debug Disable driver dependent debugging code.
netmask mask (Inet only) Specify how much of the address to reserve for subdividing net-
works 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 net-
work 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 con-
tiguous with the network portion.
dstaddr Specify the address of the correspondent on the other end of a point to
broadcast (Inet only) Specify the address to use to represent broadcasts to the net-
work. The default broadcast address is the address with a host part of all
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.
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.
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.
netstat(1), intro(4N), rc(8)
4.2 Berkeley Distribution November 16, 1996 IFCONFIG(8)