ifconfig(1M) (TCP/IP) ifconfig(1M)
NAME
ifconfig - configure network interface parameters
SYNOPSIS
ifconfig interface [ address_family ] [ address [ dest_address ] ] [
parameters ]
[ netmask mask ] [ broadcast address ] ] [ metric n ]
ifconfig interface [ protocol_family ]
DESCRIPTION
ifconfig is used to assign an address to a network interface and/or
to 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. Used without
options, ifconfig displays the current configuration for a network
interface. 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.
The interface parameter is a string of the form name unit, for
example 3740. The interface name -a is reserved, and causes the
remainder of the arguments to be applied to each address of each
interface in turn.
Since an interface may receive transmissions in differing protocols,
each of which may require separate naming schemes, the parameters and
addresses are interpreted according to the rules of some address
family, specified by the address_family parameter. The address
families currently supported are ether and inet. If no address
family is specified, inet is assumed.
For the DARPA Internet family (inet), the address is either a host
name present in the host name data base [see hosts(4)], or a DARPA
Internet address expressed in the Internet standard dot notation.
Typically, an Internet address specified in dot notation will consist
of your system's network number and the machine's unique host number.
A typical Internet address is 192.9.200.44, where 192.9.200 is the
network number and 44 is the machine's host number.
For the ether address family, the address is an Ethernet address
represented as x:x:x:x:x:x where x is a hexadecimal number between 0
and ff. Only the super-user may use the ether address family.
If the dest_address parameter is supplied in addition to the address
parameter, it specifies the address of the correspondent on the other
end of a point to point link.
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ifconfig(1M) (TCP/IP) ifconfig(1M)
OPTIONS
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 (inet only) Enable the use of a trailer link level
encapsulation when sending. If a network interface
supports trailer encapsulation, 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. This feature is
machine-dependent, and therefore not recommended. On
networks that support the Address Resolution Protocol
[see arp(7)]; currently, only 10 Mb/s Ethernet), this
flag indicates that the system should request that
other systems use trailer encapsulation when sending
to this host. Similarly, trailer encapsulations will
be used when sending to other hosts that have made
such requests.
-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(1M)]. Higher metrics have the effect of
making a route less favorable; metrics are counted as
addition hops to the destination network or host.
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
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ifconfig(1M) (TCP/IP) ifconfig(1M)
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(4). 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. If a + (plus sign) is given for the
netmask value, then the network number is looked up in
the /etc/netmasks file.
broadcast address
(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 0's. A
+ (plus sign) given for the broadcast value causes the
broadcast address to be reset to a default appropriate
for the (possibly new) Internet address and netmask.
Note that the arguments of ifconfig are interpreted
left to right, and therefore
ifconfig -a netmask + broadcast +
and
ifconfig -a broadcast + netmask +
may result in different values being assigned for the
interfaces' broadcast addresses.
EXAMPLES
If your workstation is not attached to an Ethernet and the name of
this interface is 3740, then it should be marked down as follows:
ifconfig 3740 down
To reset each interface's broadcast address after the netmasks have
been correctly set, use
ifconfig -a broadcast +
FILES
/etc/netmasks
SEE ALSO
netstat(1M), netmasks(4).
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ifconfig(1M) (TCP/IP) ifconfig(1M)
DIAGNOSTICS
Messages indicating the specified interface does not exist, the
requested address is unknown, or the user is not privileged and tried
to alter an interface's configuration.
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