ifconfig(1M) SYSTEM ADMINISTRATION COMMANDS 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 inter-
face.
The interface parameter is a string of the form name unit,
for example emd1. 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 fam-
ily 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.
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ifconfig(1M) SYSTEM ADMINISTRATION COMMANDS ifconfig(1M)
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.
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 inter-
face 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 dis-
able reception as well. This action does not
automatically disable routes using the inter-
face.
trailers (inet only) Enable the use of a trailer link
level encapsulation when sending. If a net-
work interface supports trailer encapsula-
tion, the system will, when possible, encap-
sulate 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 Pro-
tocol 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.
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ifconfig(1M) SYSTEM ADMINISTRATION COMMANDS ifconfig(1M)
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 addi-
tion 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 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 con-
tiguous 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, the emd1
interface should be marked down as follows:
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ifconfig(1M) SYSTEM ADMINISTRATION COMMANDS ifconfig(1M)
ifconfig emd1 down
To print out the addressing information for each interface,
use
ifconfig -a
To reset each interface's broadcast address after the net-
masks have been correctly set, use
ifconfig -a broadcast +
FILES
/dev/nit
/etc/netmasks
SEE ALSO
netstat(1M), netmasks(4).
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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