configure network interface parameters
/etc/ifconfig interface [ -p ]
[ address_family ]
[ address [ dest_address ] ]
[ parameters ]
ifconfig assigns an address to a network
interface and/or configures 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.
interface argument is a string of the form
name unit, for example, ``en0'' or ``lo0''.
An interface may receive transmissions in differing
protocols, each of which may require separate naming
schemes. The address_family provides for specifying
a family of protocols, and this specification may change the
interpretation of the remaining arguments. Currently only
the Internet address family is supported: thus, the only
valid value for address_family is ``inet.''
For the Internet family, the address is
either a host name present in the host name data base,
or an Internet address expressed in the
Internet standard ``dot notation''.
The dest_address is
the address of the correspondent on the other end
of a point-to-point link.
ifconfig displays the current configuration for a
network interface when no optional parameters are
causes information about all
configured interfaces to be displayed
executes slink to link this interface into the TCP/IP stack
if the interface is not already linked when ifconfig tries to set
the interface address.
This option should be used only in TCP startup scripts.
It is required for a small number of network cards to which an interface
cannot be linked
until TCP/IP is running and available to download microcode to the card
when the driver is opened.
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 reinitialized.
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.
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.
Remove the specified alias.
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 Internet addresses and
10Mb/s Ethernet addresses. This option is not applicable
in the STREAMS environment. Use of arp
for an interface is specified in /etc/strcf. The
arp driver will be opened when the
STREAMS stack is built.
Disable the use of the Address Resolution Protocol.
Set the routing metric of the interface to n,
default 0. The routing metric is used by the routing
Higher metrics have the effect of making a route less
favorable; metrics are counted as additional hops to the
destination network or host.
Set the Maximum Transfer Unit (MTU) size of the interface to
This should not normally be done except for debugging purposes.
Note that no validity checking is performed on the
specified MTU value; this
means that the unwary administrator can raise
the MTU of an interface
to a value larger than allowed by the hardware.
Enable driver dependent debugging code; usually, this turns on
extra console error logging.
is used to specify a debugging level.
Specifying level 0 turns off debugging.
(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
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.
(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.
onepacket size count
Enable the one-packet mode of operation (used for
interfaces that cannot handle back-to-back packets). The
keyword onepacket must be followed by two numeric
parameters: size specifies the small packet size in bytes and
count specifies the small packet threshold.
If small packet detection is not desired,
these values should be zero. See
for an explanation of one-packet mode.
Disable one-packet mode.
perf recv_size send_size use_fullsize
Tune interface-specific performance parameters.
must be followed by three numeric parameters:
specifies the receive window that TCP will use when
using this interface;
specifies the send window that TCP will use when using this interface;
if use_fullsize has a value of 0, then
TCP will truncate the segment
size to a multiple of 1K
when using this interface; with fast Ethernet hardware, for example, this
will cause 1460 byte segments to be used if possible. Specifying
use_fullsize with a value of 1 does not truncate
the segment size.
Enables the first link-specific parameter.
Enables the second link-specific parameter.
Enables the third link-specific parameter.
Disables the first link-specific parameter.
Disables the second link-specific parameter.
Disables the third link-specific parameter.
The debug and link-specific parameters are driver dependent and may or may
not produce any useful results when used on a given interface. See
for a discussion of any functionality that a generic kernel may support.
Only the root may modify the configuration of a network interface.
Messages indicating the
specified interface does not exist, or the requested
address is unknown, or the user is not privileged and tried
to alter an interface's configuration.
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003