IFCONFIG(ADMN) UNIX System V
Name
ifconfig - configure network interface parameters
Syntax
/etc/ifconfig interface address_family [ address
[ dest_address ] ] [ parameters ]
/etc/ifconfig interface [ protocol_family ]
Description
ifconfig is used to assign an address to a network interface
and/or configure network interface parameters; it defines
the network address of each interface present on a machine.
ifconfig is run at system start-up time via tcp(1M).
ifconfig may be run at other times to redefine an
interface's address or other operating parameters. (For
example, slattach(ADMN) also runs ifconfig.)
The interface parameter is a string of the form ``name
unit'', for example, ``en0''.
Since an interface may receive transmissions in differing
protocols, each of which may require a separate naming
scheme, it is necessary to specify the address_family, which
may change the interpretation of the remaining parameters.
Currently, only the Internet address family is supported:
thus, the only valid value for address_family is inet.
For the DARPA-Internet family, the address is either a host
name or a DARPA Internet address expressed in the Internet
standard ``dot notation''. (Host name translation is
performed either by the name server or by an entry in
/etc/hosts. [See named(ADMN) and hosts(ADMN).] Internet
``dot notation'' is described in hosts(ADMN) and inet(ADMP).
Other address families may use different notations.)
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.
detach Remove an interface from the system. This
command is applicable to transient interfaces
only, such as serial line interfaces.
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 that minimizes
the number of memory-to-memory copy
operations performed by the receiver. On
networks that support the Address Resolution
Protocol (see arp(ADMP); 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. This is 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. 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.
-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. 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(SFF). 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.
dstaddr 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.
onepacket 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, giving
the small packet size and threshold,
respectively. If small packet detection is
not desired, these values should be zero.
See tcp(ADMP) for an explanation on one-
packet mode.
-onepacket Disable one-packet mode.
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 superuser 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.
Files
/etc/slattach
calls ifconfig to start serial lines
See Also
arp(ADMN), tcp(ADMN), netstat(TC), hosts(SFF),
networks(SFF), strcf(ADMN), arp(ADMP), tcp(ADMP).
(printed 8/17/89) IFCONFIG(ADMN)