IFCONFIG(8)IFCONFIG(8)NAMEifconfig - configure network interface parameters
SYNOPSISifconfig interface address_family [ address [ dest_address ] ] [ param‐
eters ]
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. ``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'', ``iso'', 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.
For the ISO family, addresses are specified as a long hexadecimal
string, as in the Xerox family. However, two consecutive dots imply a
zero byte, and the dots are optional, if the user wishes to (carefully)
count out long strings of digits in network byte order.
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 auto‐
matically when setting the first address on an inter‐
face. 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 mes‐
sages through that interface. If possible, the inter‐
face 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 encapsula‐
tion when sending (default). If a network interface
supports trailers, the system will, when possible,
encapsulate outgoing messages in a manner which mini‐
mizes the number of memory to memory copy operations
performed by the receiver. On networks that support the
Address Resolution Protocol (see arp(4P); 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 encapsu‐
lations 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 encapsula‐
tion.
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 Eth‐
ernet 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(8c)). 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 and Iso) 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-nota‐
tion Internet address, or with a pseudo-network name
listed in the network table networks(5). The mask con‐
tains 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.
ipdst This is used to specify an Internet host who is willing
to receive ip packets encapsulating NS packets bound for
a remote network. An apparent point to point link is
constructed, and the address specified will be taken as
the NS address and network of the destination. IP
encapsulation of CLNP packets is done differently, see
eon(5).
alias Establish an additional network address for this inter‐
face. This is sometimes useful when changing network
numbers, and one wishes to accept packets addressed to
the old interface.
delete Remove the network address specified. This would be
used if you incorrectly specified an alias, or it was no
longer needed. If you have incorrectly set an NS
address having the side effect of specifying the host
portion, removing all NS addresses will allow you to
respecify the host portion.
nsellength n (ISO only) This specifies a trailing number of bytes for
a received NSAP used for local identification, the
remaining leading part of which is taken to be the NET
(Network Entity Title). The default value is 1, which
is conformant to US GOSIP. When an iso address is set
in an ifconfig command, it is really the NSAP which is
being specified. For example, in US GOSIP, 20 hex dig‐
its should be specified in the ISO NSAP to be assigned
to the interface. There is some evidence that a number
different 1 may be useful for AFI 37 type addresses.
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 pro‐
tocol family.
Only the super-user may modify the configuration of a network inter‐
face.
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.
SEE ALSOnetstat(1), netintro(4), rc(8), routed(8), eon(5)4.2 Berkeley Distribution June 24, 1990 IFCONFIG(8)